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Mark D B Eldridge - One of the best experts on this subject based on the ideXlab platform.
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paternally inherited genetic markers reveal new insights into genetic structuring within Macropus fuliginosus and hybridisation with sympatric Macropus giganteus
Australian Journal of Zoology, 2013Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B EldridgeAbstract:There are several aspects of biology in which the contribution of males and females is unequal. In these instances the examination of Y chromosome markers may be used to elucidate male-specific attributes. Here, male dispersal patterns and genetic structuring were examined using four Y-microsatellite loci in 186 male western grey kangaroos, Macropus fuliginosus, from throughout the species’ trans-continental distribution. In addition, 52 male grey kangaroos were examined to investigate hybridisation between M. fuliginosus and the eastern grey kangaroo, Macropus giganteus, in their region of sympatry in eastern Australia. Detected Y chromosome diversity was low, resulting from low effective male population size due to skewed sex ratios and a polygynous mating system. As expected, male dispersal was high across the range. However, the Lake Torrens–Flinders Ranges region appears to have significantly restricted male movement between eastern and central/western Australia. There was little evidence to suggest that other barriers (Nullarbor Plain and Swan River Valley) previously identified by nuclear and mitochondrial DNA marker studies restrict male movement. Hence, the admixture events previously identified may be associated with high male dispersal. Within the region of sympatry between M. fuliginosus and M. giganteus in eastern Australia, four M. giganteus individuals were found to possess M. fuliginosus Y-haplotypes. These results confirm the occurrence of hybridisation between male M. fuliginosus and female M. giganteus. Additionally, the introgression of M. fuliginosus Y-haplotypes into M. giganteus populations indicates that at least some male hybrids are fertile, despite evidence to the contrary from captive studies. This study has provided insights into the male contribution to population history, structure and hybridisation in M. fuliginosus, which were not predicted by comparisons between biparentally and maternally inherited markers. This highlights the importance of direct examination of the Y chromosome to provide novel insights into male-mediated processes, especially where the contribution of the sexes may differ.
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impact of pleistocene aridity oscillations on the population history of a widespread vagile australian mammal Macropus fuliginosus
Journal of Biogeography, 2012Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B EldridgeAbstract:Aim: Climatic fluctuations during the Pleistocene have shaped the population structure of many extant taxa. However, few studies have examined widespread species inhabiting the Australian continent, where periods of increased aridity characterized the Pleistocene. Here we investigate the phylogeography and population history of a widespread and vagile southern Australian marsupial, the western grey kangaroo (Macropus fuliginosus). Location: Southern Australia. Methods: We examined the variation of the mitochondrial DNA (mtDNA) control region from 511 individuals of M. fuliginosus sampled throughout their transcontinental distribution. Maximum likelihood and Bayesian analyses were used to investigate the phylogeography and coalescence analyses were then used to test hypothesized biogeographical scenarios. Results: The combined results of the phylogeographical and coalescence analyses revealed a complex evolutionary history. Macropus fuliginosus originated in the south-west of the continent, with north-western and south-western populations subsequently diverging as a result of vicariance events during the mid-Pleistocene. Subsequent arid phases affected these populations differently. In the north-west, the expansion and contraction of the arid zone resulted in repeated vicariance events and multiple divergent north-western mtDNA subclades. In contrast, the south-western population was less impacted by climatic oscillations but gave rise to a major transcontinental eastward expansion. Main conclusions: Macropus fuliginosus exhibits the genetic signature of divergence due to unidentified barriers in south-western Western Australia, while previously identified barriers across southern Australia appear to have had little impact despite evidence of a broad-scale range expansion prior to the Last Glacial Maximum (LGM). This pattern of localized expansion and contraction is comparable to unglaciated regions in both the Northern and Southern Hemispheres. Furthermore, this study indicates that despite the potential similarities between Northern Hemisphere glaciation and the activation of dune systems in the Australian arid zone, both of which rendered large areas inhospitable, the biotic responses and resultant phylogeographical signatures are dissimilar. Whereas a limited number of major geographically concordant refugia are observed in glaciated areas, the Southern Hemisphere arid zone appears to be associated with multiple species-specific idiosyncratic refugia.
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landscape discontinuities influence gene flow and genetic structure in a large vagile australian mammal Macropus fuliginosus
Molecular Ecology, 2009Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B Eldridge, Desmond W CooperAbstract:Large vagile mammals typically exhibit little genetic structuring across their range, particularly when their habitat is essentially continuous. We investigated the population genetic structure of a large vagile Australian macropodid, Macropus fuliginosus, which is continuously distributed across most of southern Australia, using nine highly polymorphic nuclear microsatellite loci. Five distinct genetic units were identified across the range, four on the mainland and one on Kangaroo Island. In addition to the predicted historic Nullarbor Plain Barrier, two unexpected mainland barriers to gene flow were identified. Both were associated with landscape discontinuities (Swan River, Flinders Ranges), which appear within the dispersal capabilities of M. fuliginosus. Typical of large vagile mammals, M. fuliginosus displays high genetic diversity (with the exception of an insular population) and weak genetic structuring (within genetic units). However, the expansion of M. fuliginosus from southwestern Australia during the Pleistocene has resulted in significantly reduced genetic diversity in eastern populations. No significant sex-biased dispersal was detected, although differences in habitat, densities and climatic conditions between the eastern and western regions of the range appear to influence dispersal with the effects of isolation by distance only evident in the west. These results suggest that the biogeography of southern Australia is more complex than previously thought and reveal that seemingly minor landscape features can significantly impact genetic structuring in large vagile mammals.
Linda E Neaves - One of the best experts on this subject based on the ideXlab platform.
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paternally inherited genetic markers reveal new insights into genetic structuring within Macropus fuliginosus and hybridisation with sympatric Macropus giganteus
Australian Journal of Zoology, 2013Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B EldridgeAbstract:There are several aspects of biology in which the contribution of males and females is unequal. In these instances the examination of Y chromosome markers may be used to elucidate male-specific attributes. Here, male dispersal patterns and genetic structuring were examined using four Y-microsatellite loci in 186 male western grey kangaroos, Macropus fuliginosus, from throughout the species’ trans-continental distribution. In addition, 52 male grey kangaroos were examined to investigate hybridisation between M. fuliginosus and the eastern grey kangaroo, Macropus giganteus, in their region of sympatry in eastern Australia. Detected Y chromosome diversity was low, resulting from low effective male population size due to skewed sex ratios and a polygynous mating system. As expected, male dispersal was high across the range. However, the Lake Torrens–Flinders Ranges region appears to have significantly restricted male movement between eastern and central/western Australia. There was little evidence to suggest that other barriers (Nullarbor Plain and Swan River Valley) previously identified by nuclear and mitochondrial DNA marker studies restrict male movement. Hence, the admixture events previously identified may be associated with high male dispersal. Within the region of sympatry between M. fuliginosus and M. giganteus in eastern Australia, four M. giganteus individuals were found to possess M. fuliginosus Y-haplotypes. These results confirm the occurrence of hybridisation between male M. fuliginosus and female M. giganteus. Additionally, the introgression of M. fuliginosus Y-haplotypes into M. giganteus populations indicates that at least some male hybrids are fertile, despite evidence to the contrary from captive studies. This study has provided insights into the male contribution to population history, structure and hybridisation in M. fuliginosus, which were not predicted by comparisons between biparentally and maternally inherited markers. This highlights the importance of direct examination of the Y chromosome to provide novel insights into male-mediated processes, especially where the contribution of the sexes may differ.
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impact of pleistocene aridity oscillations on the population history of a widespread vagile australian mammal Macropus fuliginosus
Journal of Biogeography, 2012Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B EldridgeAbstract:Aim: Climatic fluctuations during the Pleistocene have shaped the population structure of many extant taxa. However, few studies have examined widespread species inhabiting the Australian continent, where periods of increased aridity characterized the Pleistocene. Here we investigate the phylogeography and population history of a widespread and vagile southern Australian marsupial, the western grey kangaroo (Macropus fuliginosus). Location: Southern Australia. Methods: We examined the variation of the mitochondrial DNA (mtDNA) control region from 511 individuals of M. fuliginosus sampled throughout their transcontinental distribution. Maximum likelihood and Bayesian analyses were used to investigate the phylogeography and coalescence analyses were then used to test hypothesized biogeographical scenarios. Results: The combined results of the phylogeographical and coalescence analyses revealed a complex evolutionary history. Macropus fuliginosus originated in the south-west of the continent, with north-western and south-western populations subsequently diverging as a result of vicariance events during the mid-Pleistocene. Subsequent arid phases affected these populations differently. In the north-west, the expansion and contraction of the arid zone resulted in repeated vicariance events and multiple divergent north-western mtDNA subclades. In contrast, the south-western population was less impacted by climatic oscillations but gave rise to a major transcontinental eastward expansion. Main conclusions: Macropus fuliginosus exhibits the genetic signature of divergence due to unidentified barriers in south-western Western Australia, while previously identified barriers across southern Australia appear to have had little impact despite evidence of a broad-scale range expansion prior to the Last Glacial Maximum (LGM). This pattern of localized expansion and contraction is comparable to unglaciated regions in both the Northern and Southern Hemispheres. Furthermore, this study indicates that despite the potential similarities between Northern Hemisphere glaciation and the activation of dune systems in the Australian arid zone, both of which rendered large areas inhospitable, the biotic responses and resultant phylogeographical signatures are dissimilar. Whereas a limited number of major geographically concordant refugia are observed in glaciated areas, the Southern Hemisphere arid zone appears to be associated with multiple species-specific idiosyncratic refugia.
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landscape discontinuities influence gene flow and genetic structure in a large vagile australian mammal Macropus fuliginosus
Molecular Ecology, 2009Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B Eldridge, Desmond W CooperAbstract:Large vagile mammals typically exhibit little genetic structuring across their range, particularly when their habitat is essentially continuous. We investigated the population genetic structure of a large vagile Australian macropodid, Macropus fuliginosus, which is continuously distributed across most of southern Australia, using nine highly polymorphic nuclear microsatellite loci. Five distinct genetic units were identified across the range, four on the mainland and one on Kangaroo Island. In addition to the predicted historic Nullarbor Plain Barrier, two unexpected mainland barriers to gene flow were identified. Both were associated with landscape discontinuities (Swan River, Flinders Ranges), which appear within the dispersal capabilities of M. fuliginosus. Typical of large vagile mammals, M. fuliginosus displays high genetic diversity (with the exception of an insular population) and weak genetic structuring (within genetic units). However, the expansion of M. fuliginosus from southwestern Australia during the Pleistocene has resulted in significantly reduced genetic diversity in eastern populations. No significant sex-biased dispersal was detected, although differences in habitat, densities and climatic conditions between the eastern and western regions of the range appear to influence dispersal with the effects of isolation by distance only evident in the west. These results suggest that the biogeography of southern Australia is more complex than previously thought and reveal that seemingly minor landscape features can significantly impact genetic structuring in large vagile mammals.
Shane K Maloney - One of the best experts on this subject based on the ideXlab platform.
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estimating the age of western grey kangaroos Macropus fuliginosus ocydromus
Australian Mammalogy, 2017Co-Authors: Chris Mayberry, Roberta Bencini, Peter R Mawson, Shane K MaloneyAbstract:Scientific studies and population management may benefit from knowledge of the age structure of a target population. We evaluated traditional and newly developed methods of estimating the age of kangaroos with data from 336 western grey kangaroos (Macropus fuliginosus) culled from a wild population in south-western Australia. We compared their ages based on molar progression with data on head, leg, and foot length, a balanced sum of all three measures, dried eye-lens weight, and molar wear score, and derived formulae to estimate age from each variable. Molar wear score has a linear relationship to molar progression and therefore leads to similar estimations of age, but requires only one complete arcade of molars. Because the relationships between age and the lengths of head, foot and leg are curvilinear, these become less reliable indicators of age with increasing age but the accuracy can be improved by considering a combination of the lengths of head, foot, and leg. Estimation of age from dried lens weight is more accurate than estimation from morphometry. The use of morphometry to estimate the age of kangaroos older than two years is more reliable than previously thought and requisite data can be collected from live animals. Where lethal methods are needed to collect samples, a largely intact skull, a single arcade of molars, or the lens extracted from one eye can reliably be used to estimate age.
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scaling of the ankle extensor muscle tendon units and the biomechanical implications for bipedal hopping locomotion in the post pouch kangaroo Macropus fuliginosus
Journal of Anatomy, 2017Co-Authors: Andrew A Biewener, Edward P Snelling, David A Taggart, Andrea Fuller, Duncan Mitchell, Shane K Maloney, Roger S SeymourAbstract:Bipedal hopping is used by macropods, including rat-kangaroos, wallabies and kangaroos (superfamily Macropodoidea). Interspecific scaling of the ankle extensor muscle-tendon units in the lower hindlimbs of these hopping bipeds shows that peak tendon stress increases disproportionately with body size. Consequently, large kangaroos store and recover more strain energy in their tendons, making hopping more efficient, but their tendons are at greater risk of rupture. This is the first intraspecific scaling analysis on the functional morphology of the ankle extensor muscle-tendon units (gastrocnemius, plantaris and flexor digitorum longus) in one of the largest extant species of hopping mammal, the western grey kangaroo Macropus fuliginosus (5.8–70.5 kg post-pouch body mass). The effective mechanical advantage of the ankle extensors does not vary with post-pouch body mass, scaling with an exponent not significantly different from 0.0. Therefore, larger kangaroos balance rotational moments around the ankle by generating muscle forces proportional to weight-related gravitational forces. Maximum force is dependent upon the physiological cross-sectional area of the muscle, which we found scales geometrically with a mean exponent of only 0.67, rather than 1.0. Therefore, larger kangaroos are limited in their capacity to oppose large external forces around the ankle, potentially compromising fast or accelerative hopping. The strain energy return capacity of the ankle extensor tendons increases with a mean exponent of ~1.0, which is much shallower than the exponent derived from interspecific analyses of hopping mammals (~1.4–1.9). Tendon safety factor (ratio of rupture stress to estimated peak hopping stress) is lowest in the gastrocnemius (< 2), and it decreases with body mass with an exponent of −0.15, extrapolating to a predicted rupture at 160 kg. Extinct giant kangaroos weighing 250 kg could therefore not have engaged in fast hopping using ‘scaled-up’ lower hindlimb morphology of extant western grey kangaroos.
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Western grey kangaroos (Macropus fuliginosus) include fauna underpasses in their home range
Wildlife Research, 2016Co-Authors: Paul D. Chachelle, Roberta Bencini, Brian Chambers, Shane K MaloneyAbstract:Context The presence of large mammals on roads poses a serious risk to both the animals and motorists if collisions with vehicles occur. Fencing roads can reduce this risk, and it also limits the landscape-scale movements of animals. By also constructing fauna underpasses it may be possible to avoid collisions with vehicles, while, at the same time, allowing the natural movement of animals across the landscape. Aims We aimed to determine whether western grey kangaroos (Macropus fulignosus) would use fauna underpasses and to determine how this may affect their home range. Methods We used motion-activated infrared cameras to monitor the use of one large 8 × 3 m arched underpass and two 0.9-m-diameter fauna underpasses over 342 days between March 2011 and March 2012. The underpasses were situated between reserves separated by a four-lane fenced highway, with one reserve surrounded by residential properties. At the same time, 20 kangaroos (10 males and 10 females) were radio-tracked to determine the size of their home range and to test whether the animals incorporated the fauna underpasses into their daily movements. Key results The large fauna underpass was used 3116 times by individual kangaroos in groups of up to 21 animals, whereas the two smaller underpasses were used only twice. In total, 14 of the 20 radio-collared kangaroos used the large underpass over the course of the study, but underpass use did not affect home-range size. Kangaroos that did not use the underpass had a significantly higher proportion of their home range on residential properties surrounding one of the reserves than did those kangaroos that used the underpass. Conclusions The use of the underpass did not affect the size of the home range of the kangaroos, but it allowed the kangaroos to access grazing areas that would have been otherwise inaccessible. Fauna underpasses allow the safe passage of kangaroos between isolated remnant vegetation patches and may reduce significantly the risks posed to motorists and kangaroos from collisions. Implications Fencing roads and constructing fauna underpasses is a viable solution to reducing some of the problems of managing large kangaroos in peri-urban areas.
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biphasic allometry of cardiac growth in the developing kangaroo Macropus fuliginosus
Physiological and Biochemical Zoology, 2015Co-Authors: Edward P Snelling, David A Taggart, Shane K Maloney, Anthony P Farrell, Roger S SeymourAbstract:AbstractInterspecific studies of adult mammals show that heart mass (Mh, g) increases in direct proportion to body mass (Mb, kg), such that Mh ∝ Mb1.00. However, intraspecific studies on heart mass in mammals at different stages of development reveal considerable variation between species, Mh ∝ Mb0.70–1.00. Part of this variation may arise as a result of the narrow body size range of growing placental mammals, from birth to adulthood. Marsupial mammals are born relatively small and offer an opportunity to examine the ontogeny of heart mass over a much broader body size range. Data from 29 western grey kangaroos Macropus fuliginosus spanning 800-fold in body mass (0.084–67.5 kg) reveal the exponent for heart mass decreases significantly when the joey leaves the pouch (ca. 5–6 kg body mass). In the pouch, the heart mass of joeys scales with hyperallometry, Mh(in-pouch) = 6.39Mb1.10 ± 0.05, whereas in free-roaming juveniles and adults, heart mass scales with hypoallometry, Mh(postpouch) = 14.2Mb0.77 ± 0.08. ...
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scaling of left ventricle cardiomyocyte ultrastructure across development in the kangaroo Macropus fuliginosus
The Journal of Experimental Biology, 2015Co-Authors: Edward P Snelling, David A Taggart, Shane K Maloney, Anthony P Farrell, C M Leigh, Lyn Waterhouse, Ruth Williams, Roger S SeymourAbstract:ABSTRACT The heart and left ventricle of the marsupial western grey kangaroo Macropus fuliginosus exhibit biphasic allometric growth, whereby a negative shift in the trajectory of cardiac growth occurs at pouch exit. In this study, we used transmission electron microscopy to examine the scaling of left ventricle cardiomyocyte ultrastructure across development in the western grey kangaroo over a 190-fold body mass range (0.355−67.5 kg). The volume-density (%) of myofibrils, mitochondria, sarcoplasmic reticuli and T-tubules increase significantly during in-pouch growth, such that the absolute volume (ml) of these organelles scales with body mass ( M b ; kg) with steep hyperallometry: 1.41 M b 1.38 , 0.64 M b 1.29 , 0.066 M b 1.45 and 0.035 M b 1.87 , respectively. Maturation of the left ventricle ultrastructure coincides with pouch vacation, as organelle volume-densities scale independent of body mass across post-pouch development, such that absolute organelle volumes scale in parallel and with relatively shallow hypoallometry: 4.65 M b 0.79 , 1.75 M b 0.77 , 0.21 M b 0.79 and 0.35 M b 0.79 , respectively. The steep hyperallometry of organelle volumes and volume-densities across in-pouch growth is consistent with the improved contractile performance of isolated cardiac muscle during fetal development in placental mammals, and is probably critical in augmenting cardiac output to levels necessary for endothermy and independent locomotion in the young kangaroo as it prepares for pouch exit. The shallow hypoallometry of organelle volumes during post-pouch growth suggests a decrease in relative cardiac requirements as body mass increases in free-roaming kangaroos, which is possibly because the energy required for hopping is independent of speed, and the capacity for energy storage during hopping could increase as the kangaroo grows.
Roger S Seymour - One of the best experts on this subject based on the ideXlab platform.
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Ontogenetic scaling of the gastrointestinal tract of a marsupial foregut fermenter, the western grey kangaroo Macropus fuliginosus melanops
Journal of Comparative Physiology B, 2021Co-Authors: Adam J. Munn, Edward P Snelling, David A Taggart, Roger S SeymourAbstract:As an animal grows, the relative sizes of their organs may grow proportionately or disproportionately, depending on ontogenetic changes in function. If organ growth is proportional (isometric), then the exponent of the scaling equation is 1.0. Relative decreases or increases in size result in exponents less than 1 (hypoallometric) or greater than 1 (hyperallometric). Thus, the empirical exponent can indicate potential changes in function. The entire gastrointestinal tract (GIT) of the foregut-fermenting western grey kangaroo Macropus fuliginosus melanops exhibited biphasic allometry across five orders of magnitude body mass (M_b; 52.0 g–70.5 kg) . Prior to weaning at around 12 kg M_b, the entire empty GIT mass scaled with hyperallometry (M_b^1.13), shifting to hypoallometry (M_b^0.80) post-weaning. In addition, there were varying patterns of hyper-, hypo-, and isometric scaling for select GIT organs, with several displaying phase shifts associated with major life-history events, specifically around exit from the maternal pouch and around weaning. Mass of the kangaroo forestomach, the main fermentation site, scaled with hyperallometry (M_b^1.16) before the stage of increased vegetation intake, and possibly after this stage (M_b^1.12; P = 0.07), accompanied by a higher scaling factor (elevation of the curve) probably associated with more muscle for processing fibrous vegetation. The acid hindstomach mass showed hyperallometry (M_b^1.15) before weaning, but hypoallometry (M_b ^0.58) post-weaning, presumably associated with decreasing intake of milk. Small intestine mass and length each scaled isometrically throughout ontogeny, with no discernible breakpoints at any life-history stage. The caecum and colon mass were steeply hyperallometric early in-pouch life (M_b^1.59–1.66), when the young were ectothermic, hairless, and supported solely by milk. After around 295 g M_b, caecum mass remained hyperallometric (M_b^1.14), possibly supporting its early development as a nidus for microbial populations to provide for secondary fermentation in this organ after the young transition from milk to vegetation.
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scaling of the ankle extensor muscle tendon units and the biomechanical implications for bipedal hopping locomotion in the post pouch kangaroo Macropus fuliginosus
Journal of Anatomy, 2017Co-Authors: Andrew A Biewener, Edward P Snelling, David A Taggart, Andrea Fuller, Duncan Mitchell, Shane K Maloney, Roger S SeymourAbstract:Bipedal hopping is used by macropods, including rat-kangaroos, wallabies and kangaroos (superfamily Macropodoidea). Interspecific scaling of the ankle extensor muscle-tendon units in the lower hindlimbs of these hopping bipeds shows that peak tendon stress increases disproportionately with body size. Consequently, large kangaroos store and recover more strain energy in their tendons, making hopping more efficient, but their tendons are at greater risk of rupture. This is the first intraspecific scaling analysis on the functional morphology of the ankle extensor muscle-tendon units (gastrocnemius, plantaris and flexor digitorum longus) in one of the largest extant species of hopping mammal, the western grey kangaroo Macropus fuliginosus (5.8–70.5 kg post-pouch body mass). The effective mechanical advantage of the ankle extensors does not vary with post-pouch body mass, scaling with an exponent not significantly different from 0.0. Therefore, larger kangaroos balance rotational moments around the ankle by generating muscle forces proportional to weight-related gravitational forces. Maximum force is dependent upon the physiological cross-sectional area of the muscle, which we found scales geometrically with a mean exponent of only 0.67, rather than 1.0. Therefore, larger kangaroos are limited in their capacity to oppose large external forces around the ankle, potentially compromising fast or accelerative hopping. The strain energy return capacity of the ankle extensor tendons increases with a mean exponent of ~1.0, which is much shallower than the exponent derived from interspecific analyses of hopping mammals (~1.4–1.9). Tendon safety factor (ratio of rupture stress to estimated peak hopping stress) is lowest in the gastrocnemius (< 2), and it decreases with body mass with an exponent of −0.15, extrapolating to a predicted rupture at 160 kg. Extinct giant kangaroos weighing 250 kg could therefore not have engaged in fast hopping using ‘scaled-up’ lower hindlimb morphology of extant western grey kangaroos.
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femoral bone perfusion through the nutrient foramen during growth and locomotor development of western grey kangaroos Macropus fuliginosus
The Journal of Experimental Biology, 2017Co-Authors: T J N Nelson, Edward P Snelling, Roger S SeymourAbstract:ABSTRACT The nutrient artery passes through the nutrient foramen on the shaft of the femur and supplies more than half of the total blood flow to the bone. Assuming that the size of the nutrient foramen correlates with the size of the nutrient artery, an index of blood flow rate ( Q i ) can be calculated from nutrient foramen dimensions. Interspecific Q i is proportional to locomotor activity levels in adult mammals, birds and reptiles. However, no studies have yet estimated intraspecific Q i to test for the effects of growth and locomotor development on bone blood flow requirements. In this study, we used micro-CT and medical CT scanning to measure femoral dimensions and foramen radius to calculate femoral Q i during the in-pouch and post-pouch life stages of western grey kangaroos ( Macropus fuliginosus ) weighing 5.7 g to 70.5 kg and representing a 12,350-fold range in body mass. A biphasic scaling relationship between Q i and body mass was observed (breakpoint at ca. 1–5 kg body mass right before permanent pouch exit), with a steep exponent of 0.96±0.09 (95% CI) during the in-pouch life stage and a statistically independent exponent of –0.59±0.90 during the post-pouch life stage. In-pouch joeys showed Q i values that were 50–100 times higher than those of adult diprotodont marsupials of the same body mass, but gradually converged with them as post-pouch adults. Bone modelling during growth appears to be the main determinant of femoral bone blood flow during in-pouch development, whereas bone remodelling for micro-fracture repair due to locomotion gradually becomes the main determinant when kangaroos leave the pouch and become more active.
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biphasic allometry of cardiac growth in the developing kangaroo Macropus fuliginosus
Physiological and Biochemical Zoology, 2015Co-Authors: Edward P Snelling, David A Taggart, Shane K Maloney, Anthony P Farrell, Roger S SeymourAbstract:AbstractInterspecific studies of adult mammals show that heart mass (Mh, g) increases in direct proportion to body mass (Mb, kg), such that Mh ∝ Mb1.00. However, intraspecific studies on heart mass in mammals at different stages of development reveal considerable variation between species, Mh ∝ Mb0.70–1.00. Part of this variation may arise as a result of the narrow body size range of growing placental mammals, from birth to adulthood. Marsupial mammals are born relatively small and offer an opportunity to examine the ontogeny of heart mass over a much broader body size range. Data from 29 western grey kangaroos Macropus fuliginosus spanning 800-fold in body mass (0.084–67.5 kg) reveal the exponent for heart mass decreases significantly when the joey leaves the pouch (ca. 5–6 kg body mass). In the pouch, the heart mass of joeys scales with hyperallometry, Mh(in-pouch) = 6.39Mb1.10 ± 0.05, whereas in free-roaming juveniles and adults, heart mass scales with hypoallometry, Mh(postpouch) = 14.2Mb0.77 ± 0.08. ...
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scaling of left ventricle cardiomyocyte ultrastructure across development in the kangaroo Macropus fuliginosus
The Journal of Experimental Biology, 2015Co-Authors: Edward P Snelling, David A Taggart, Shane K Maloney, Anthony P Farrell, C M Leigh, Lyn Waterhouse, Ruth Williams, Roger S SeymourAbstract:ABSTRACT The heart and left ventricle of the marsupial western grey kangaroo Macropus fuliginosus exhibit biphasic allometric growth, whereby a negative shift in the trajectory of cardiac growth occurs at pouch exit. In this study, we used transmission electron microscopy to examine the scaling of left ventricle cardiomyocyte ultrastructure across development in the western grey kangaroo over a 190-fold body mass range (0.355−67.5 kg). The volume-density (%) of myofibrils, mitochondria, sarcoplasmic reticuli and T-tubules increase significantly during in-pouch growth, such that the absolute volume (ml) of these organelles scales with body mass ( M b ; kg) with steep hyperallometry: 1.41 M b 1.38 , 0.64 M b 1.29 , 0.066 M b 1.45 and 0.035 M b 1.87 , respectively. Maturation of the left ventricle ultrastructure coincides with pouch vacation, as organelle volume-densities scale independent of body mass across post-pouch development, such that absolute organelle volumes scale in parallel and with relatively shallow hypoallometry: 4.65 M b 0.79 , 1.75 M b 0.77 , 0.21 M b 0.79 and 0.35 M b 0.79 , respectively. The steep hyperallometry of organelle volumes and volume-densities across in-pouch growth is consistent with the improved contractile performance of isolated cardiac muscle during fetal development in placental mammals, and is probably critical in augmenting cardiac output to levels necessary for endothermy and independent locomotion in the young kangaroo as it prepares for pouch exit. The shallow hypoallometry of organelle volumes during post-pouch growth suggests a decrease in relative cardiac requirements as body mass increases in free-roaming kangaroos, which is possibly because the energy required for hopping is independent of speed, and the capacity for energy storage during hopping could increase as the kangaroo grows.
Kyall R Zenger - One of the best experts on this subject based on the ideXlab platform.
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paternally inherited genetic markers reveal new insights into genetic structuring within Macropus fuliginosus and hybridisation with sympatric Macropus giganteus
Australian Journal of Zoology, 2013Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B EldridgeAbstract:There are several aspects of biology in which the contribution of males and females is unequal. In these instances the examination of Y chromosome markers may be used to elucidate male-specific attributes. Here, male dispersal patterns and genetic structuring were examined using four Y-microsatellite loci in 186 male western grey kangaroos, Macropus fuliginosus, from throughout the species’ trans-continental distribution. In addition, 52 male grey kangaroos were examined to investigate hybridisation between M. fuliginosus and the eastern grey kangaroo, Macropus giganteus, in their region of sympatry in eastern Australia. Detected Y chromosome diversity was low, resulting from low effective male population size due to skewed sex ratios and a polygynous mating system. As expected, male dispersal was high across the range. However, the Lake Torrens–Flinders Ranges region appears to have significantly restricted male movement between eastern and central/western Australia. There was little evidence to suggest that other barriers (Nullarbor Plain and Swan River Valley) previously identified by nuclear and mitochondrial DNA marker studies restrict male movement. Hence, the admixture events previously identified may be associated with high male dispersal. Within the region of sympatry between M. fuliginosus and M. giganteus in eastern Australia, four M. giganteus individuals were found to possess M. fuliginosus Y-haplotypes. These results confirm the occurrence of hybridisation between male M. fuliginosus and female M. giganteus. Additionally, the introgression of M. fuliginosus Y-haplotypes into M. giganteus populations indicates that at least some male hybrids are fertile, despite evidence to the contrary from captive studies. This study has provided insights into the male contribution to population history, structure and hybridisation in M. fuliginosus, which were not predicted by comparisons between biparentally and maternally inherited markers. This highlights the importance of direct examination of the Y chromosome to provide novel insights into male-mediated processes, especially where the contribution of the sexes may differ.
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impact of pleistocene aridity oscillations on the population history of a widespread vagile australian mammal Macropus fuliginosus
Journal of Biogeography, 2012Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B EldridgeAbstract:Aim: Climatic fluctuations during the Pleistocene have shaped the population structure of many extant taxa. However, few studies have examined widespread species inhabiting the Australian continent, where periods of increased aridity characterized the Pleistocene. Here we investigate the phylogeography and population history of a widespread and vagile southern Australian marsupial, the western grey kangaroo (Macropus fuliginosus). Location: Southern Australia. Methods: We examined the variation of the mitochondrial DNA (mtDNA) control region from 511 individuals of M. fuliginosus sampled throughout their transcontinental distribution. Maximum likelihood and Bayesian analyses were used to investigate the phylogeography and coalescence analyses were then used to test hypothesized biogeographical scenarios. Results: The combined results of the phylogeographical and coalescence analyses revealed a complex evolutionary history. Macropus fuliginosus originated in the south-west of the continent, with north-western and south-western populations subsequently diverging as a result of vicariance events during the mid-Pleistocene. Subsequent arid phases affected these populations differently. In the north-west, the expansion and contraction of the arid zone resulted in repeated vicariance events and multiple divergent north-western mtDNA subclades. In contrast, the south-western population was less impacted by climatic oscillations but gave rise to a major transcontinental eastward expansion. Main conclusions: Macropus fuliginosus exhibits the genetic signature of divergence due to unidentified barriers in south-western Western Australia, while previously identified barriers across southern Australia appear to have had little impact despite evidence of a broad-scale range expansion prior to the Last Glacial Maximum (LGM). This pattern of localized expansion and contraction is comparable to unglaciated regions in both the Northern and Southern Hemispheres. Furthermore, this study indicates that despite the potential similarities between Northern Hemisphere glaciation and the activation of dune systems in the Australian arid zone, both of which rendered large areas inhospitable, the biotic responses and resultant phylogeographical signatures are dissimilar. Whereas a limited number of major geographically concordant refugia are observed in glaciated areas, the Southern Hemisphere arid zone appears to be associated with multiple species-specific idiosyncratic refugia.
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landscape discontinuities influence gene flow and genetic structure in a large vagile australian mammal Macropus fuliginosus
Molecular Ecology, 2009Co-Authors: Linda E Neaves, Kyall R Zenger, Robert I T Prince, Mark D B Eldridge, Desmond W CooperAbstract:Large vagile mammals typically exhibit little genetic structuring across their range, particularly when their habitat is essentially continuous. We investigated the population genetic structure of a large vagile Australian macropodid, Macropus fuliginosus, which is continuously distributed across most of southern Australia, using nine highly polymorphic nuclear microsatellite loci. Five distinct genetic units were identified across the range, four on the mainland and one on Kangaroo Island. In addition to the predicted historic Nullarbor Plain Barrier, two unexpected mainland barriers to gene flow were identified. Both were associated with landscape discontinuities (Swan River, Flinders Ranges), which appear within the dispersal capabilities of M. fuliginosus. Typical of large vagile mammals, M. fuliginosus displays high genetic diversity (with the exception of an insular population) and weak genetic structuring (within genetic units). However, the expansion of M. fuliginosus from southwestern Australia during the Pleistocene has resulted in significantly reduced genetic diversity in eastern populations. No significant sex-biased dispersal was detected, although differences in habitat, densities and climatic conditions between the eastern and western regions of the range appear to influence dispersal with the effects of isolation by distance only evident in the west. These results suggest that the biogeography of southern Australia is more complex than previously thought and reveal that seemingly minor landscape features can significantly impact genetic structuring in large vagile mammals.
