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Jiří Neustupa - One of the best experts on this subject based on the ideXlab platform.
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habitat preferences of micrasterias arcuata Desmidiales viridiplantae in wetlands from central brazil an allometric study
Hydrobiologia, 2019Co-Authors: Barbara Medeiros Fonseca, Lidia Mendes Feijo, Jiří NeustupaAbstract:The green alga Micrasterias arcuata is commonly found in the periphyton of slightly acidic ponds and wet grasslands of central Brazil. We used M. arcuata complex as a model system for evaluation of the following questions: (a) Is there any relation between morphological characteristics of M. arcuata populations and ecological features of the sites? (b) Can the observed plasticity be explained by an allometric scaling relationship leading to differential distribution of the morphotypes among different habitats (ponds and wet grasslands)? (c) Is there any surface-to-volume ratio (S:V) scaling that can be explained as adaptive response to ecological characteristics of sites? A total of 50 individual semicells of M. arcuata were photographed from ten natural populations, yielding a 500 objects dataset. Individuals from ponds were morphologically different from the ones in the wet grasslands, presenting bigger cells, but also with higher S:V. The eventual surface loss usually associated to bigger sizes was compensated by more elaborated cells, yielding positive allometry of the S:V ratio scaling. Our data support the idea that such differences in cell morphology are an adaptation to environmental conditions, especially desiccation stress favoring cells with lower S:V and higher isoperimetric quotient in the wet grasslands.
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Host specificity of epiphytic diatom (Bacillariophyceae) and desmid (Desmidiales) communities
Aquatic Ecology, 2016Co-Authors: Petra Thea Mutinová, Jiří Neustupa, Stanislao Bevilacqua, Antonio TerlizziAbstract:The nature of the relationships between host plants and associated microalgal epiphyton in freshwater ecosystems is largely undetermined. Many studies assume that the host plant, as a biologically active substrate, must have a direct influence on associated epiphytic communities, whereas other studies favor the view that host plants are a neutral substrate with only indirect effects on epiphytic communities. Here, we addressed the question of whether host plant taxonomic identity influences epiphyton community structure in comparison with other factors (which also provided further insight into the general ecology of freshwater microphytobenthos) by examining four types of natural plant substrates at five freshwater sites in the Czech Republic. The results demonstrated that host plant type significantly affected epiphytic community structure; most notably, the genus Sphagnum was found to support remarkably different epiphytic communities, probably including several microalgal substrate specialists. Other host plants we examined included Utricularia spp., Nymphaea spp., and Potamogeton natans L., all of which were presumably neutral substrates. The differences among the host plants varied among sites, however, suggesting the presence of an interaction between these two factors. Thus, we concluded that host plants may not always provide a neutral substrate for microalgal epiphyton and, consequently, biomonitoring surveys should account for variation relating to this factor. Finally, our work showed that epiphytic diatoms (Bacillariophyceae) and desmids (Desmidiales) adopted similar group strategies, thus allowing for generalizations of patterns across entire microphytobentic communities.
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Static allometry of unicellular green algae: scaling of cellular surface area and volume in the genus Micrasterias (Desmidiales).
Journal of evolutionary biology, 2015Co-Authors: Jiří NeustupaAbstract:The surface area-to-volume ratio of cells is one of the key factors affecting fundamental biological processes and, thus, fitness of unicellular organisms. One of the general models for allometric increase in surface-to-volume scaling involves fractal-like elaboration of cellular surfaces. However, specific data illustrating this pattern in natural populations of the unicellular organisms have not previously been available. This study shows that unicellular green algae of the genus Micrasterias (Desmidiales) have positive allometric surface-to-volume scaling caused by changes in morphology of individual species, especially in the degree of cell lobulation. This allometric pattern was also detected within most of the cultured and natural populations analysed. Values of the allometric S:V scaling within individual populations were closely correlated to the phylogenetic structure of the clade. In addition, they were related to species-specific cellular morphology. Individual populations differed in their allometric patterns, and their position in the allometric space was strongly correlated with the degree of allometric S:V scaling. This result illustrates that allometric shape patterns are an important correlate of the capacity of individual populations to compensate for increases in their cell volumes by increasing the surface area. However, variation in allometric patterns was not associated with phylogenetic structure. This indicates that the position of the populations in the allometric space was not evolutionarily conserved and might be influenced by environmental factors.
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Spatio-temporal community structure of peat bog benthic desmids on a microscale
Aquatic Ecology, 2012Co-Authors: Jiří Neustupa, Kateřina Černá, Jan Št’astnýAbstract:Significant spatial variation in species composition of microphytobenthos often occurs at scales of decimetres. This microscale variation is typically more connected with dispersal-related events than to environmental factors. In this study, 4 microscale transects were delimited at 4 temperate lowland peat bog localities to investigate spatial and temporal microscale variations in benthic desmids (Desmidiales, Viridiplantae). Significant spatial autocorrelation was detected in most of the transects taken 3 times, in September and December 2010 and March 2011. The relative abundance of species data produced more pronounced spatial patterns than the presence–absence data. Spatial autocorrelation mostly decreased during the winter period, possibly due to meteorological disturbances, resulting in less spatially structured phytobenthic community in the March transects. In most cases, spatial distance accounted for a significant part of the variation in a community structure, even in analyses that controlled for the effects of environmental and temporal factors. This indicated that pure spatial factors should be considered important for structuring phytobenthic communities, even across a temporal time span of 6 months. The reduced data sets that included only 25 % of the most frequented species produced very similar patterns in spatial and temporal autocorrelation as the full data sets. Consequently, we concluded that microscale variation of benthic desmids may be sufficiently represented by dynamics of the common species.
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A multilocus phylogeny of the desmid genus Micrasterias (Streptophyta): Evidence for the accelerated rate of morphological evolution in protists
Molecular phylogenetics and evolution, 2011Co-Authors: Pavel Škaloud, Kateřina Černá, Katarína Nemjová, Jana Veselá, Jiří NeustupaAbstract:Micrasterias, the name of which is derived from the Greek for 'little star', comprises possibly the most spectacularly shaped desmids (Desmidiales, Streptophyta). Presently, the genus Micrasterias includes about 60 traditional species, the majority of which were described in the early 19th century. We used a comprehensive multigene dataset (including SSU rDNA, psaA, and coxIII loci) of 34 Micrasterias taxa to assess the relationships between individual morphological species. The resulting phylogeny was used to assess the patterns characterizing the morphological evolution of this genus. The phylogenetic analysis led to the recognition of eight well-resolved lineages that could be characterized by selected morphological features. Apart from the members of Micrasterias, three species belonged to different traditional desmid genera (Cosmarium, Staurodesmus, and Triploceras) and were inferred to be nested within the genus. Morphological comparisons of these species with their relatives revealed an accelerated rate of morphological evolution. Mapping morphological diversification of the genus on the phylogenetic tree revealed profound differences in the phylogenetic signal of selected phenotypic features. Whereas the branching pattern of the cells clearly correlated with the phylogeny, cell complexity possibly reflected rather their adaptive morphological responses to environmental conditions. Finally, ancestral reconstruction of distribution patterns indicated potential origin of the genus in North America, with additional speciation events occurring in the Indo-Malaysian region.
Carlos Eduardo De Mattos Bicudo - One of the best experts on this subject based on the ideXlab platform.
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morphological variation in staurastrum rotula zygnemaphyceae Desmidiales in the deepest natural brazilian lake essence or accident
Brazilian Journal of Biology, 2014Co-Authors: Luciana Gomes Barbosa, G J M Araujo, Francisco A. R. Barbosa, Carlos Eduardo De Mattos BicudoAbstract:For many decades, polymorphism and its consequences have only been studied from the taxonomic point of view. Presently, interest has switched to the environmental causes of morphological variation and its consequences in the form and essence of the species. This study aimed at evaluating desmids morphological modifications of Staurastrum rotula Nordstedt during inter-annual succession patterns in two warm monomitic tropical lakes: Dom Helvecio (19°45′- 19°48′45″S, 42°33′45″W) and Carioca (19°45′20″S, 42°37′12″W). The effect of thermal stability and light and nutrients availability was based on samples collected monthly from January 2002 to December 2006 compared the morphological modifications. Results indicated that morphological variation, asexual reproduction, theratological forms, mucilaginous envelope and fungal infection were highest in Lake Dom Helvecio and coincided with the biomass increase of species with complex morphology between September and March (stratification period). The Zmix oscillation, wind and rainfall occurring at the end of the mixing period and beginning of the stratification were suggested as autochthonous and allochthonous disturbance agents, respectively, identified as inducers of asexual reproduction and consequently of the morphological variation. It was suggested that incidence of parasitism may act as a potential controlling agent for the Staurastrum rotula population size. It was concluded that morphological variation represents accidents in the original form, i.e. in the desmid species essence, promoting the existence of ecoforms, not of new infraspecific taxa.
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Morphological variation in Staurastrum rotula (Zygnemaphyceae, Desmidiales) in the deepest natural Brazilian lake: essence or accident?
Brazilian journal of biology = Revista brasleira de biologia, 2014Co-Authors: Luciana Gomes Barbosa, G J M Araujo, Francisco A. R. Barbosa, Carlos Eduardo De Mattos BicudoAbstract:For many decades, polymorphism and its consequences have only been studied from the taxonomic point of view. Presently, interest has switched to the environmental causes of morphological variation and its consequences in the form and essence of the species. This study aimed at evaluating desmids morphological modifications of Staurastrum rotula Nordstedt during inter-annual succession patterns in two warm monomitic tropical lakes: Dom Helvécio (19°45'- 19°48'45″S, 42°33'45″W) and Carioca (19°45'20″S, 42°37'12″W). The effect of thermal stability and light and nutrients availability was based on samples collected monthly from January 2002 to December 2006 compared the morphological modifications. Results indicated that morphological variation, asexual reproduction, theratological forms, mucilaginous envelope and fungal infection were highest in Lake Dom Helvécio and coincided with the biomass increase of species with complex morphology between September and March (stratification period). The Zmix oscillation, wind and rainfall occurring at the end of the mixing period and beginning of the stratification were suggested as autochthonous and allochthonous disturbance agents, respectively, identified as inducers of asexual reproduction and consequently of the morphological variation. It was suggested that incidence of parasitism may act as a potential controlling agent for the Staurastrum rotula population size. It was concluded that morphological variation represents accidents in the original form, i.e. in the desmid species essence, promoting the existence of ecoforms, not of new infraspecific taxa.
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Genus Octacanthium (Zygnemaphyceae, Desmidiaceae) in the State of São Paulo, Brazil
Biota Neotropica, 2003Co-Authors: Sílvia Maria Mathes Faustino, Carlos Eduardo De Mattos BicudoAbstract:A floristic survey was based on the study of 148 sample units, from which 75 were already deposited at the Herbario Cientifico do Estado “Maria Eneyda P. Kauffmann Fidalgo” of the Instituto de Botânica, Sao Paulo State Department of Environment, and 73 were collected during the period 2000-2001. Three taxa of Octacanthium (Desmidiales, Zygnemaphyceae) were identified: O. bifidum (Brebisson) Compere var. bifidum, O. mucronulatum (Nordstedt) Compere var. mucronulatum, and O. octocorne (Ralfs) Compere var. octocorne.
Kenneth G. Karol - One of the best experts on this subject based on the ideXlab platform.
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Phylogeny of the conjugating green algae based on chloroplast and mitochondrial nucleotide sequence data
Journal of Phycology, 2008Co-Authors: John D. Hall, Kenneth G. Karol, Richard M. Mccourt, Charles F. DelwicheAbstract:The conjugating green algae represent a lineage of charophyte green algae known for their structural diversity and unusual mode of sexual reproduction, conjugation. These algae are ubiquitous in freshwater environments, where they are often important primary producers, but few studies have investigated evolutionary relationships in a molecular systematic context. A 109-taxon data set consisting of three gene fragments (two from the chloroplast and one from the mitochondrial genome) was used to estimate the phylogeny of the genera of the conjugating green algae. Maximum likelihood (ML), maximum parsimony (MP), and Bayesian inference (BI) were used to estimate relationships from the 4,047 alignable nucleotides. This study confirmed the polyphyly of the Zygnemataceae and Mesotaeniaceae with respect to one another. The Peniaceae were determined to be paraphyletic, and two genera traditionally classified among the Zygnematales appear to belong to the lineage that gave rise to the Desmidiales. Six genera, Euastrum, Cosmarium, Cylindrocystis, Mesotaenium, Spondylosium, and Staurodesmus, were polyphyletic in this analysis. These findings have important implications for the evolution of structural characteristics in the group and will require some taxonomic changes. More work will be required to delineate lineages of Zygnematales in particular and to identify structural synapomorphies for some of the newly identified clades.
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phylogeny of the conjugating green algae zygnematales and Desmidiales based on plastid and mitochondrial gene sequences
Journal of Phycology, 2002Co-Authors: Richard M. Mccourt, D A Hewitt, J. Park, Kenneth G. KarolAbstract:The conjugating green algae (Order Zygnematales and Desmidiales) are charophyceans, that is, they are among the green algae most closely related to land plants. Compared to the five other groups of charophyceans (Mesostigma, Klebsormidiales, Chlorokybales, Coleochaetales, Charales), the conjugating greens are by far the most diverse taxonomically (6 families, about 55 genera, 3–4000 species) and very widespread in distribution (including common species such as Spirogyra, Zygnema, Cosmarium, and Staurastrum). Thallus shape ranges from simple, oblong unicells (saccoderm desmids, or Mesotaeniaceae), to unbranched filaments of cells with smooth walls (Zygnemataceae), to elaborately ornate and deeply incised unicells or filaments made of such cells (placoderm desmids, in four families). Prior analyses of sequences of the chloroplast-encoded gene rbcL (1354 bp, or 95% of the gene) sampled from all six families showed that two of the traditional families (saccoderms and filamentous forms) are paraphyletic, i.e. they do not form two independent clades, although the component genera may together constitute a monophyletic group. In contrast, three families of placoderm desmids formed three monophyletic groups within a larger clade. New analyses using partial sequences from the mitochondrial gene coxIII (608 bp, or 76% of the gene) for 21 species of conjugating green algae from all six families supported the conclusions of the rbcL analysis, although bootstrap support for each gene along was weak for many branches. The coxIII sequences are more variable than rbcL and have proportionately more parsimony-informative sites (43% vs. 34%, respectively). Combining the two genes improved the resolution of the resulting tree: (1) bootstrap support increased for all branches, particularly in regards relationships of placoderm desmids; and (2) monophyly of a clade containing filamentous and saccoderm desmids was strongly supported. We conclude that phylogeny of conjugating green algae will be much improved by sampling from additional genes.
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phylogeny of gonatozygon and genicularia gonatozygaceae Desmidiales based on rbcl sequences
European Journal of Phycology, 1996Co-Authors: Nellie E Park, Kenneth G. Karol, Robert W Hoshaw, Richard M. MccourtAbstract:Gonatozygon and Genicularia have been placed in various families within the conjugating green algae, and recent treatments place them in the order Desmidiales, in a separate family Gonatozygaceae or within the family Peniaceae. Nucleotide sequences of the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) were determined for these genera and included in an analysis with published sequences for related genera in the families Zygnemataceae (filamentous conjugating green algae) and Mesotaeniaceae (saccoderm desmids), as well as charophycean and other outgroups. Gonatozygon and Genicularia form a strongly supported monophyletic group that is closely related to the saccoderm desmid, Roya. These three genera form a clade within a paraphyletic assemblage of genera from the Mesotaeniaceae and Zygnemataceae. The rbcL data suggest a close relationship of Roya with Gonatozygon and Genicularia, which is not supported by studies of cell wall ultrastructure but is congruent with some studies of pig...
Richard M. Mccourt - One of the best experts on this subject based on the ideXlab platform.
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Phylogeny of the conjugating green algae based on chloroplast and mitochondrial nucleotide sequence data
Journal of Phycology, 2008Co-Authors: John D. Hall, Kenneth G. Karol, Richard M. Mccourt, Charles F. DelwicheAbstract:The conjugating green algae represent a lineage of charophyte green algae known for their structural diversity and unusual mode of sexual reproduction, conjugation. These algae are ubiquitous in freshwater environments, where they are often important primary producers, but few studies have investigated evolutionary relationships in a molecular systematic context. A 109-taxon data set consisting of three gene fragments (two from the chloroplast and one from the mitochondrial genome) was used to estimate the phylogeny of the genera of the conjugating green algae. Maximum likelihood (ML), maximum parsimony (MP), and Bayesian inference (BI) were used to estimate relationships from the 4,047 alignable nucleotides. This study confirmed the polyphyly of the Zygnemataceae and Mesotaeniaceae with respect to one another. The Peniaceae were determined to be paraphyletic, and two genera traditionally classified among the Zygnematales appear to belong to the lineage that gave rise to the Desmidiales. Six genera, Euastrum, Cosmarium, Cylindrocystis, Mesotaenium, Spondylosium, and Staurodesmus, were polyphyletic in this analysis. These findings have important implications for the evolution of structural characteristics in the group and will require some taxonomic changes. More work will be required to delineate lineages of Zygnematales in particular and to identify structural synapomorphies for some of the newly identified clades.
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phylogeny of the conjugating green algae zygnematales and Desmidiales based on plastid and mitochondrial gene sequences
Journal of Phycology, 2002Co-Authors: Richard M. Mccourt, D A Hewitt, J. Park, Kenneth G. KarolAbstract:The conjugating green algae (Order Zygnematales and Desmidiales) are charophyceans, that is, they are among the green algae most closely related to land plants. Compared to the five other groups of charophyceans (Mesostigma, Klebsormidiales, Chlorokybales, Coleochaetales, Charales), the conjugating greens are by far the most diverse taxonomically (6 families, about 55 genera, 3–4000 species) and very widespread in distribution (including common species such as Spirogyra, Zygnema, Cosmarium, and Staurastrum). Thallus shape ranges from simple, oblong unicells (saccoderm desmids, or Mesotaeniaceae), to unbranched filaments of cells with smooth walls (Zygnemataceae), to elaborately ornate and deeply incised unicells or filaments made of such cells (placoderm desmids, in four families). Prior analyses of sequences of the chloroplast-encoded gene rbcL (1354 bp, or 95% of the gene) sampled from all six families showed that two of the traditional families (saccoderms and filamentous forms) are paraphyletic, i.e. they do not form two independent clades, although the component genera may together constitute a monophyletic group. In contrast, three families of placoderm desmids formed three monophyletic groups within a larger clade. New analyses using partial sequences from the mitochondrial gene coxIII (608 bp, or 76% of the gene) for 21 species of conjugating green algae from all six families supported the conclusions of the rbcL analysis, although bootstrap support for each gene along was weak for many branches. The coxIII sequences are more variable than rbcL and have proportionately more parsimony-informative sites (43% vs. 34%, respectively). Combining the two genes improved the resolution of the resulting tree: (1) bootstrap support increased for all branches, particularly in regards relationships of placoderm desmids; and (2) monophyly of a clade containing filamentous and saccoderm desmids was strongly supported. We conclude that phylogeny of conjugating green algae will be much improved by sampling from additional genes.
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phylogeny of gonatozygon and genicularia gonatozygaceae Desmidiales based on rbcl sequences
European Journal of Phycology, 1996Co-Authors: Nellie E Park, Kenneth G. Karol, Robert W Hoshaw, Richard M. MccourtAbstract:Gonatozygon and Genicularia have been placed in various families within the conjugating green algae, and recent treatments place them in the order Desmidiales, in a separate family Gonatozygaceae or within the family Peniaceae. Nucleotide sequences of the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) were determined for these genera and included in an analysis with published sequences for related genera in the families Zygnemataceae (filamentous conjugating green algae) and Mesotaeniaceae (saccoderm desmids), as well as charophycean and other outgroups. Gonatozygon and Genicularia form a strongly supported monophyletic group that is closely related to the saccoderm desmid, Roya. These three genera form a clade within a paraphyletic assemblage of genera from the Mesotaeniaceae and Zygnemataceae. The rbcL data suggest a close relationship of Roya with Gonatozygon and Genicularia, which is not supported by studies of cell wall ultrastructure but is congruent with some studies of pig...
Pavel Škaloud - One of the best experts on this subject based on the ideXlab platform.
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DNA Content Variation and Its Significance in the Evolution of the Genus Micrasterias (Desmidiales, Streptophyta)
PloS one, 2014Co-Authors: Aloisie Poulíèková, Petra Mazalová, Radim J. Vašut, Petra Šarhanová, Jiøí Neustupa, Pavel ŠkaloudAbstract:It is now clear that whole genome duplications have occurred in all eukaryotic evolutionary lineages, and that the vast majority of flowering plants have experienced polyploidisation in their evolutionary history. However, study of genome size variation in microalgae lags behind that of higher plants and seaweeds. In this study, we have addressed the question whether microalgal phylogeny is associated with DNA content variation in order to evaluate the evolutionary significance of polyploidy in the model genus Micrasterias. We applied flow-cytometric techniques of DNA quantification to microalgae and mapped the estimated DNA content along the phylogenetic tree. Correlations between DNA content and cell morphometric parameters were also tested using geometric morphometrics. In total, DNA content was successfully determined for 34 strains of the genus Micrasterias. The estimated absolute 2C nuclear DNA amount ranged from 2.1 to 64.7 pg; intraspecific variation being 17.4-30.7 pg in M. truncata and 32.0-64.7 pg in M. rotata. There were significant differences between DNA contents of related species. We found strong correlation between the absolute nuclear DNA content and chromosome numbers and significant positive correlation between the DNA content and both cell size and number of terminal lobes. Moreover, the results showed the importance of cell/life cycle studies for interpretation of DNA content measurements in microalgae.
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A multilocus phylogeny of the desmid genus Micrasterias (Streptophyta): Evidence for the accelerated rate of morphological evolution in protists
Molecular phylogenetics and evolution, 2011Co-Authors: Pavel Škaloud, Kateřina Černá, Katarína Nemjová, Jana Veselá, Jiří NeustupaAbstract:Micrasterias, the name of which is derived from the Greek for 'little star', comprises possibly the most spectacularly shaped desmids (Desmidiales, Streptophyta). Presently, the genus Micrasterias includes about 60 traditional species, the majority of which were described in the early 19th century. We used a comprehensive multigene dataset (including SSU rDNA, psaA, and coxIII loci) of 34 Micrasterias taxa to assess the relationships between individual morphological species. The resulting phylogeny was used to assess the patterns characterizing the morphological evolution of this genus. The phylogenetic analysis led to the recognition of eight well-resolved lineages that could be characterized by selected morphological features. Apart from the members of Micrasterias, three species belonged to different traditional desmid genera (Cosmarium, Staurodesmus, and Triploceras) and were inferred to be nested within the genus. Morphological comparisons of these species with their relatives revealed an accelerated rate of morphological evolution. Mapping morphological diversification of the genus on the phylogenetic tree revealed profound differences in the phylogenetic signal of selected phenotypic features. Whereas the branching pattern of the cells clearly correlated with the phylogeny, cell complexity possibly reflected rather their adaptive morphological responses to environmental conditions. Finally, ancestral reconstruction of distribution patterns indicated potential origin of the genus in North America, with additional speciation events occurring in the Indo-Malaysian region.