The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform

David M. Rowell - One of the best experts on this subject based on the ideXlab platform.

  • Short‐range phenotypic divergence among genetically distinct parapatric populations of an Australian funnel‐web spider
    Ecology and Evolution, 2017
    Co-Authors: Mark K. L. Wong, James D. Woodman, David M. Rowell
    Abstract:

    Speciation involves divergence at genetic and phenotypic levels. Where substantial genetic differentiation exists among populations, examining variation in multiple phenotypic characters may elucidate the mechanisms by which divergence and speciation unfold. Previous work on the Australian funnel-web spider Atrax sutherlandi Gray (2010; Records of the Australian Museum 62, 285–392; Mygalomorphae: Hexathelidae: Atracinae) has revealed a marked genetic structure along a 110-kilometer transect, with six genetically distinct, parapatric populations attributable to past glacial cycles. In the present study, we explore variation in three classes of phenotypic characters (metabolic rate, water loss, and morphological traits) within the context of this phylogeographic structuring. Variation in metabolic and water loss rates shows no detectable association with genetic structure; the little variation observed in these rates may be due to the spiders’ behavioral adaptations (i.e., burrowing), which buffer the effects of climatic gradients across the landscape. However, of 17 morphological traits measured, 10 show significant variation among genetic populations, in a disjunct manner that is clearly not latitudinal. Moreover, patterns of variation observed for morphological traits serving different organismic functions (e.g., prey capture, burrowing, and locomotion) are dissimilar. In contrast, a previous study of an ecologically similar sympatric spider with little genetic structure indicated a strong latitudinal response in 10 traits over the same range. The congruence of morphological variation with deep phylogeographic structure in Tallaganda's A. sutherlandi populations, as well as the inconsistent patterns of variation across separate functional traits, suggest that the spiders are likely in early stages of speciation, with parapatric populations independently responding to local selective forces.

  • Short-range phenotypic divergence among genetically distinct parapatric populations of an Australian funnel-web spider.
    Ecology and evolution, 2017
    Co-Authors: Mark K. L. Wong, James D. Woodman, David M. Rowell
    Abstract:

    Speciation involves divergence at genetic and phenotypic levels. Where substantial genetic differentiation exists among populations, examining variation in multiple phenotypic characters may elucidate the mechanisms by which divergence and speciation unfold. Previous work on the Australian funnel-web spider Atrax sutherlandi Gray (2010; Records of the Australian Museum 62, 285–392; Mygalomorphae: Hexathelidae: Atracinae) has revealed a marked genetic structure along a 110-kilometer transect, with six genetically distinct, parapatric populations attributable to past glacial cycles. In the present study, we explore variation in three classes of phenotypic characters (metabolic rate, water loss, and morphological traits) within the context of this phylogeographic structuring. Variation in metabolic and water loss rates shows no detectable association with genetic structure; the little variation observed in these rates may be due to the spiders’ behavioral adaptations (i.e., burrowing), which buffer the effects of climatic gradients across the landscape. However, of 17 morphological traits measured, 10 show significant variation among genetic populations, in a disjunct manner that is clearly not latitudinal. Moreover, patterns of variation observed for morphological traits serving different organismic functions (e.g., prey capture, burrowing, and locomotion) are dissimilar. In contrast, a previous study of an ecologically similar sympatric spider with little genetic structure indicated a strong latitudinal response in 10 traits over the same range. The congruence of morphological variation with deep phylogeographic structure in Tallaganda's A. sutherlandi populations, as well as the inconsistent patterns of variation across separate functional traits, suggest that the spiders are likely in early stages of speciation, with parapatric populations independently responding to local selective forces.

  • Temporal variation in venom yield of the Australian funnel-web spider Atrax sutherlandi (Hexathelidae: Atracinae)
    Arachnology, 2016
    Co-Authors: Mark K. L. Wong, James D. Woodman, David M. Rowell
    Abstract:

    Summary Temporal variation in the venom yield of spiders is a relatively poorly understood phenomenon. We investigated temporal variation in venom yield of the Australian funnel-web spider Atrax sutherlandi Gray 2010 (Hexathelidae: Atracinae). The venom yield of spiders collected and milked in winter was 62.9% higher than those collected and milked in autumn, despite all undergoing acclimatization (45 days in darkness at 10°C and 100%RH) before milking. Our findings highlight the potential effects of seasonality on spider venoms and lay the groundwork for future studies to investigate the evolutionary and ecological correlates of this phenomenon further.

  • Microhabitat preferences drive phylogeographic disparities in two Australian funnel web spiders
    Biological Journal of the Linnean Society, 2011
    Co-Authors: Amber S. Beavis, Paul Sunnucks, David M. Rowell
    Abstract:

    Comparative phylogeography is underpinned by the assumption that sympatrically-distributed taxa will have experienced similar environmental histories, resulting in broadly congruent spatial structuring of phylogenetic lineages, particularly if they inhabit similar niches. However, divergent local conditions, specifically those related to microhabitat, may produce significantly divergent systematic signatures of demographic histories. In the present study, we compare the phylogenetic and population genetic spatial patterns displayed by two species of niche-separated (but sympatrically distributed) Australian funnel web spiders (Mygalomorphae: Hexathelidae). We demonstrate that an apparently minor disparity in habitat niche has led to divergent experiences of a common environmental history in the saproxylic Hadronyche cerberea and the ground-burrowing Atrax sutherlandi. Furthermore, we take a crucial first step in documenting the molecular systematics of a group that has traditionally suffered from a dearth of research interest. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 805–819.

  • Population structure in a saproxylic funnelweb spider (Hexathelidae: Hadronyche ) along a forested rainfall gradient
    Journal of Zoology, 2006
    Co-Authors: James D. Woodman, Julian Ash, David M. Rowell
    Abstract:

    We present research undertaken at Tallaganda State Forest, Australia, describing how current climatic conditions impact upon the saproxylic (decaying wood) habitat and the relationship between this habitat and the demography and morphology of a saproxylic funnelweb spider (Hadronyche sp.). Climatic data support a north–south habitat cline and, to a lesser extent, a short-range, aspect-driven habitat cline. Rainfall and log moisture content increased with latitude through the forest, and aspect affected the amount of solar radiation penetrating to ground level. The distribution and abundance of Hadronyche varied among sites along both clines in response to several variables. The decay state of logs was highly influential, with wet, highly decayed logs favoured over dry, hard ones. Population density was highest in wetter, southern sites where these logs were abundant, but rare, suitably decomposed logs in dry, northern sites still typically hosted a comparable number of individuals. Morphological measurements showed some phenotypic variation along the north–south habitat gradient, but not over the short-range, aspect-driven gradients. Hadronyche would not be expected to show similarly strong patterns of molecular variation as seen in saproxylic Collembola and Onychophora within Tallaganda as it appears to be more vagile.

Pablo A. Goloboff - One of the best experts on this subject based on the ideXlab platform.

Miquel A. Arnedo - One of the best experts on this subject based on the ideXlab platform.

  • Threatened or Threatening? Evidence for Independent Introductions of Macrothele calpeiana (Walckenaer, 1805) (Araneae: Hexathelidae) and First Observation of Reproduction Outside its Natural Distribution Range
    Arachnology, 2016
    Co-Authors: Adrià Bellvert, Miquel A. Arnedo
    Abstract:

    Summary Despite being endemic to the south of the Iberian Peninsula, Macrothele calpeiana has been repeatedly reported far from its native range (e.g. northern Italy, Switzerland, Belgium, Holland). Here, we confirm, using DNA barcode data, that the specimens collected in northern Catalonia, Majorca, and northern Italy are indeed recent introductions. Additionally, our data suggest that they originated from different source populations, and corroborate former suggestions that the recent expansion of Macrothele may be linked to the commercial transport of olive trees. Former species distribution modelling studies have revealed that the exotic localities reported are far from the ecological optimum of the species and hence that introduced specimens have slim chances of survival. However, a recent finding of several individuals of different sex and stages in a coastal town in northern Catalonia (northeastern Iberian Peninsula) suggests that M. calpeiana is able to reproduce outside its native range and that ...

  • From Gondwana to Europe: inferring the origins of Mediterranean Macrothele spiders (Araneae : Hexathelidae) and the limits of the family Hexathelidae
    Invertebrate Systematics, 2014
    Co-Authors: Vera Opatova, Miquel A. Arnedo
    Abstract:

    The family Hexathelidae ranks among the smaller mygalomorph spider families. Most species are endemic to the Australasian region and the family was traditionally considered an example of a Gondwanan lineage. However, recent studies have cast some doubt on the monophyly of the family. Macrothele is the only genus with an out-of-Gondwana distribution. The bulk of the Macrothele diversity is found in South-east Asia, few species are known from central Africa and two species inhabit Europe: Macrothele calpeiana (Walckenaer, 1805) from the Iberian Peninsula and Macrothele cretica Kulczynski, 1903 endemic to Crete. Here we investigate the origins of the European Macrothele species by means of a multi-locus phylogenetic approach and by inferring the time frame of the diversification of the genus using Bayesian relaxed clock methods. We also provide further insights into the phylogenetic status of the family Hexathelidae. Our results indicate that the diversification of Macrothele traces back to the period of the Gondwana break-up and its present-day distribution most likely reflects the subsequent tectonic plate movements. The two European species were not recovered as sister taxa, suggesting that Macrothele colonised the Mediterranean region twice independently. The polyphyly of the family Hexathelidae is further confirmed and the subfamily Atracinae is identified as the conflicting lineage.

  • Mitochondrial markers reveal deep population subdivision in the European protected spider Macrothele calpeiana (Walckenaer, 1805) (Araneae, Hexathelidae)
    Conservation Genetics, 2007
    Co-Authors: Miquel A. Arnedo, Miguel-angel Ferrández
    Abstract:

    The funnel-web spider genus Macrothele is the only representative of the mygalomorph family Hexathelidae not found in Australia or New Zealand. Its 26 species occur in Central Africa and the Oriental region. Two Macrothele species are found in Europe: M. cretica Kulczynski, 1903 from Crete, and M. calpeiana (Walckenaer, 1805) type species of the genus and the largest European spider, whose distribution extends across the south-eastern Iberian Peninsula, and in two localities of North Africa. Macrothele calpeiana is the only spider protected under European legislation. The fragmentation and destruction of the cork oak forest, with which M. calpeiana was thought to be closely associated, prompted the inclusion of this species in the Bern Convention. Some authors, however, have challenged this view and consider M. calpeiana to be neither a cork oak forest bioindicator nor an endangered species. By contrast, other observations suggest that the distribution of the species is extremely fragmented and that most local populations should be considered as threatened. In this paper, we examine aspects of the conservation status of M. calpeiana in the light of molecular phylogenetic analyses based on mitochondrial markers of sample specimens from major populations. Our data confirm the fragmented distribution of M. calpeiana and reveal high levels of genetic differentiation across its populations. Local population growth cannot be ruled out, though the lineage as a whole has apparently not undergone population growth. Lineage age estimates suggest that M. calpeiana colonized the Iberian Peninsula during the Messinian salinity crisis and that the current population fragmentation originates from the Pliocene and Pleistocene. We argue that the fragmentation and deep genetic divergence across populations, along with evolutionary singularity and endemicity in one of Europe’s main biodiversity hotspots, support the preservation of its legally protected status.

Jennifer M.s. Koh - One of the best experts on this subject based on the ideXlab platform.

  • Unravelling the complex venom landscapes of lethal Australian funnel-web spiders (Hexathelidae: Atracinae) using LC-MALDI-TOF mass spectrometry
    Journal of Proteomics, 2013
    Co-Authors: Alexandre Palagi, David Wilson, Jennifer Koh, Mathieu Leblanc, Sébastien Dutertre, Glenn King, Graham Nicholson, Pierre Escoubas, Jennifer M.s. Koh
    Abstract:

    Spider venoms represent vast sources of bioactive molecules whose diversity remains largely unknown. Indeed, only a small subset of species have been studied out of the ~43,000 extant spider species. The present study investigated inter- and intra-species venom complexity in 18 samples collected from a variety of lethal Australian funnel-web spiders (Mygalomorphae: Hexathelidae: Atracinae) using C4 reversed-phase separation coupled to offline MALDI-TOF mass spectrometry (LC-MALDI-TOF MS). An in-depth investigation focusing on four atracine venoms (male Illawarra wisharti, male and female Hadronyche cerberea, and female Hadronyche infensa Toowoomba) revealed, on average, ~800 peptides in female venoms while male venoms contained ~400 peptides, distributed across most HPLC fractions. This is significantly higher than previous estimates of peptide expression in mygalomorph venoms. These venoms also showed distinct intersexual as well as intra- and inter-species variation in peptide masses. Construction of both 3D and 2D contour plots revealed that peptide mass distributions in all 18 venoms were centered around the 3200-5400m/z range and to a lesser extent the 6600-8200m/z range, consistent with previously described hexatoxins. These findings highlight the extensive diversity of peptide toxins in Australian funnel-web spider venoms that that can be exploited as novel therapeutic and biopesticide lead molecules.

  • Unravelling the complex venom landscapes of lethal Australian funnel-web spiders (Hexathelidae: Atracinae) using LC-MALDI-TOF mass spectrometry.
    Journal of proteomics, 2013
    Co-Authors: Alexandre Palagi, Graham M. Nicholson, Glenn F. King, Mathieu Leblanc, Sébastien Dutertre, Jennifer M.s. Koh, Denise Wilson, Pierre Escoubas
    Abstract:

    Spider venoms represent vast sources of bioactive molecules whose diversity remains largely unknown. Indeed, only a small subset of species have been studied out of the ~. 43,000 extant spider species. The present study investigated inter- and intra-species venom complexity in 18 samples collected from a variety of lethal Australian funnel-web spiders (Mygalomorphae: Hexathelidae: Atracinae) using C4 reversed-phase separation coupled to offline MALDI-TOF mass spectrometry (LC-MALDI-TOF MS). An in-depth investigation focusing on four atracine venoms (male Illawarra wisharti, male and female Hadronyche cerberea, and female Hadronyche infensa Toowoomba) revealed, on average, ~. 800 peptides in female venoms while male venoms contained ~. 400 peptides, distributed across most HPLC fractions. This is significantly higher than previous estimates of peptide expression in mygalomorph venoms. These venoms also showed distinct intersexual as well as intra- and inter-species variation in peptide masses. Construction of both 3D and 2D contour plots revealed that peptide mass distributions in all 18 venoms were centered around the 3200-5400. m/. z range and to a lesser extent the 6600-8200. m/. z range, consistent with previously described hexatoxins. These findings highlight the extensive diversity of peptide toxins in Australian funnel-web spider venoms that that can be exploited as novel therapeutic and biopesticide lead molecules. Biological significance: In the present study we describe the complexity of 18 venoms from lethal Australian funnel-web spiders using LC-MALDI-TOF MS. The study includes an in-depth investigation, focusing on four venoms, that revealed the presence of ~. 800 peptides in female venoms and ~. 400 peptides in male venoms. This is significantly higher than previous estimates of peptide expression in spider venoms. By constructing both 3D and 2D contour plots we were also able to reveal the distinct intersexual as well as intra- and inter-species variation in venom peptide masses. We show that peptide mass distributions in all 18 venoms were centered around the 3200-5400 m/. z range and to a lesser extent the 6600-8200 m/. z range, consistent with the small number of previously described hexatoxins from these spiders. These findings highlight the extensive diversity of peptide toxins in Australian funnel-web spider venoms that that can be exploited as novel therapeutic and biopesticide lead molecules. The present study has greatly expanded our understanding of peptide variety and complexity in these lethal mygalomorph spiders. Specifically it highlights both the utility of LC-MALDI-TOF in spider taxonomy and the massive combinatorial peptide libraries that spider venoms offer the pharmaceutical and agrochemical industry.

Pierre Escoubas - One of the best experts on this subject based on the ideXlab platform.

  • Unravelling the complex venom landscapes of lethal Australian funnel-web spiders (Hexathelidae: Atracinae) using LC-MALDI-TOF mass spectrometry
    Journal of Proteomics, 2013
    Co-Authors: Alexandre Palagi, David Wilson, Jennifer Koh, Mathieu Leblanc, Sébastien Dutertre, Glenn King, Graham Nicholson, Pierre Escoubas, Jennifer M.s. Koh
    Abstract:

    Spider venoms represent vast sources of bioactive molecules whose diversity remains largely unknown. Indeed, only a small subset of species have been studied out of the ~43,000 extant spider species. The present study investigated inter- and intra-species venom complexity in 18 samples collected from a variety of lethal Australian funnel-web spiders (Mygalomorphae: Hexathelidae: Atracinae) using C4 reversed-phase separation coupled to offline MALDI-TOF mass spectrometry (LC-MALDI-TOF MS). An in-depth investigation focusing on four atracine venoms (male Illawarra wisharti, male and female Hadronyche cerberea, and female Hadronyche infensa Toowoomba) revealed, on average, ~800 peptides in female venoms while male venoms contained ~400 peptides, distributed across most HPLC fractions. This is significantly higher than previous estimates of peptide expression in mygalomorph venoms. These venoms also showed distinct intersexual as well as intra- and inter-species variation in peptide masses. Construction of both 3D and 2D contour plots revealed that peptide mass distributions in all 18 venoms were centered around the 3200-5400m/z range and to a lesser extent the 6600-8200m/z range, consistent with previously described hexatoxins. These findings highlight the extensive diversity of peptide toxins in Australian funnel-web spider venoms that that can be exploited as novel therapeutic and biopesticide lead molecules.

  • Unravelling the complex venom landscapes of lethal Australian funnel-web spiders (Hexathelidae: Atracinae) using LC-MALDI-TOF mass spectrometry.
    Journal of proteomics, 2013
    Co-Authors: Alexandre Palagi, Graham M. Nicholson, Glenn F. King, Mathieu Leblanc, Sébastien Dutertre, Jennifer M.s. Koh, Denise Wilson, Pierre Escoubas
    Abstract:

    Spider venoms represent vast sources of bioactive molecules whose diversity remains largely unknown. Indeed, only a small subset of species have been studied out of the ~. 43,000 extant spider species. The present study investigated inter- and intra-species venom complexity in 18 samples collected from a variety of lethal Australian funnel-web spiders (Mygalomorphae: Hexathelidae: Atracinae) using C4 reversed-phase separation coupled to offline MALDI-TOF mass spectrometry (LC-MALDI-TOF MS). An in-depth investigation focusing on four atracine venoms (male Illawarra wisharti, male and female Hadronyche cerberea, and female Hadronyche infensa Toowoomba) revealed, on average, ~. 800 peptides in female venoms while male venoms contained ~. 400 peptides, distributed across most HPLC fractions. This is significantly higher than previous estimates of peptide expression in mygalomorph venoms. These venoms also showed distinct intersexual as well as intra- and inter-species variation in peptide masses. Construction of both 3D and 2D contour plots revealed that peptide mass distributions in all 18 venoms were centered around the 3200-5400. m/. z range and to a lesser extent the 6600-8200. m/. z range, consistent with previously described hexatoxins. These findings highlight the extensive diversity of peptide toxins in Australian funnel-web spider venoms that that can be exploited as novel therapeutic and biopesticide lead molecules. Biological significance: In the present study we describe the complexity of 18 venoms from lethal Australian funnel-web spiders using LC-MALDI-TOF MS. The study includes an in-depth investigation, focusing on four venoms, that revealed the presence of ~. 800 peptides in female venoms and ~. 400 peptides in male venoms. This is significantly higher than previous estimates of peptide expression in spider venoms. By constructing both 3D and 2D contour plots we were also able to reveal the distinct intersexual as well as intra- and inter-species variation in venom peptide masses. We show that peptide mass distributions in all 18 venoms were centered around the 3200-5400 m/. z range and to a lesser extent the 6600-8200 m/. z range, consistent with the small number of previously described hexatoxins from these spiders. These findings highlight the extensive diversity of peptide toxins in Australian funnel-web spider venoms that that can be exploited as novel therapeutic and biopesticide lead molecules. The present study has greatly expanded our understanding of peptide variety and complexity in these lethal mygalomorph spiders. Specifically it highlights both the utility of LC-MALDI-TOF in spider taxonomy and the massive combinatorial peptide libraries that spider venoms offer the pharmaceutical and agrochemical industry.