Evolutionary Diversification of Tropical Forest Mammals and Butterflies
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Evolutionary diversification of central African forest mammals (Stephan Ntie, Anne Johnston (Davis), Iván Soto-Calderón, Richard Rouyer)
For over a century, evolutionary biologists have been intrigued by the extraordinary diversity of tropical rainforests. However, the evolutionary study of many species has been hampered by the challenges of sampling across remote areas in the tropics and the difficulties of obtaining geo-referenced DNA samples from large or elusive forest mammals. With the advent of non-invasive sampling, it is now possible to test geographically-explicit diversity hypotheses using geo-referenced fecal material. Initial findings from my work on gorilla phylogeography suggest that both Pleistocene forest refugia and rivers may shape regional patterns of genetic differentiation (Clifford et al., 2004; Anthony et al., 2007a). These findings then raise several intriguing questions: Namely, is similar geographic sub-structuring evident in other rainforest associated taxa? Do these patterns reflect a common history of Pleistocene diversification? |
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Forest duikers in the subfamily Cephalophinae represent good models for testing hypotheses of diversification due their hypothesized recent origin, widespread distribution and tight association with forested habitats. As a first step in developing an effective non-invasive sampling strategy, we determined optimal storage conditions for the PCR amplification of fecal samples (Soto-Calderon et al., 2009), established diagnostic tools for identifying duikers species from their feces (Ntie et al., 2010a) and developed several microsatellite multiplex assemblies suited to analyses of population structure in duikers and other tropical forest artiodactyls (Ntie et al., 2010b). We also challenged the routine application of DNA barcodes to identify species such as the forest duikers that have undergone a recent, rapid diversification (Johnston et al., 2011). A multi-locus analysis of species evolutionary relationships suggests that nearly all sister species originated during the Pleistocene, strongly suggesting that past forest fragmentation events may have played an important role in the radiation of this group of antelope (Johnston and Anthony, 2012). Current work aims to assess the role of hypothesized forest refugia and major rivers in shaping fine-scale genetic structure as well as assess the role of local ecological gradients in shaping intra-specific genetic structure. This work has been conducted in collaboration with researchers at the Université des Sciences et Techniques de Masuku (USTM), Mike Bruford (University of Cardiff Wales), the Wildlife Conservation Society of Gabon, and numerous other collaborators from the U.S., Europe and Africa.
Johnston A.R. and Anthony N.M. (2012) A multi-locus species phylogeny of African forest duikers in the subfamily Cephalophinae: evidence for a recent radiation in the Pleistocene. BMC Evolutionary Biology 12: 120.
Johnston A.R., Morikawa M., Ntie S. and Anthony N.M. (2011) Evaluating DNA barcoding criteria using the genus Cephalophus as a test case. Conservation Genetics 10: 251-255.
Ntie S., Johnston A., Mickala P., van Vuuren B., Bowkett A., Colyn M., Sonet G., Rouyer R., Wallace R.A., LeBlanc K., van Vliet N., Ryder O., Hymas O., Wickings E., Telfer P., Maisels F., Lahm S.A. and Anthony N.M. (2010a) A molecular diagnostic for the identification of central African artiodactyls from faeces. Animal Conservation 13: 80-93.
Ntie S., Soto-Calderon I.D. and Anthony N.M. (2010b) Assembly and cross-species amplification of three microsatellite multiplex sets in central African artiodactyls. Molecular Ecology Resources 10: 1059-1065.
Soto-Calderón I.D., Ntie S., Mickala P., Maisels F., Wickings E.J. and Anthony N.M. (2009) Effects of storage type and time on DNA amplification success in tropical ungulate faeces. Molecular Ecology Resources 9: 471-479.
Johnston A.R. and Anthony N.M. (2012) A multi-locus species phylogeny of African forest duikers in the subfamily Cephalophinae: evidence for a recent radiation in the Pleistocene. BMC Evolutionary Biology 12: 120.
Johnston A.R., Morikawa M., Ntie S. and Anthony N.M. (2011) Evaluating DNA barcoding criteria using the genus Cephalophus as a test case. Conservation Genetics 10: 251-255.
Ntie S., Johnston A., Mickala P., van Vuuren B., Bowkett A., Colyn M., Sonet G., Rouyer R., Wallace R.A., LeBlanc K., van Vliet N., Ryder O., Hymas O., Wickings E., Telfer P., Maisels F., Lahm S.A. and Anthony N.M. (2010a) A molecular diagnostic for the identification of central African artiodactyls from faeces. Animal Conservation 13: 80-93.
Ntie S., Soto-Calderon I.D. and Anthony N.M. (2010b) Assembly and cross-species amplification of three microsatellite multiplex sets in central African artiodactyls. Molecular Ecology Resources 10: 1059-1065.
Soto-Calderón I.D., Ntie S., Mickala P., Maisels F., Wickings E.J. and Anthony N.M. (2009) Effects of storage type and time on DNA amplification success in tropical ungulate faeces. Molecular Ecology Resources 9: 471-479.
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Testing hypotheses of diversification in Madagascan butterflies (Marjorie Linares, Tracy Faustermann, N. Jonathon Clark, Whitney Nolan)
The extraordinary high levels of endemic species in Madagascar make it an ideal model region for testing patterns of species diversification (Vences et. al. 2009). Several hypotheses have been proposed to explain the high species diversity of many taxonomic groups in Madagascar (Vences et. al. 2009). The western rainforest refugia hypothesis states that mesic forest relicts in the drier central plateau played a role in the isolation and subsequent diversification of rainforest-restricted taxa. Under this hypothesis we predict little genetic structure within eastern contiguous forest sites but significant structure between western forest relicts. Another popular hypothesis known as the ecogeographic constraint hypothesis argues that the transition from eastern forest to drier habitats in other regions may have led to speciation across major biomes. |
Evolutionary diversification of Madagascan butterflies in the genus Heteropsis
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In this case, population genetic structure should reflect a primarily east-west division. Lastly, the montane refugia hypothesis argues that speciation may have been driven by isolation of forest taxa into three major upland areas during periods of maximal glaciation. According to this hypothesis we expect population genetic variation to be structured by one or more major montane areas. Although several studies have been carried out in vertebrate species to test these hypotheses, their importance in shaping insect biological diversity is largely unknown.
The aim of this study is therefore to test these three major diversity hypotheses using mitochondrial sequence data obtained from multiple populations from each of six species within the butterfly genus Heteropsis that vary in their degree of forest association: H. ankaratra is a grassland generalist that is widely distributed across the island. H. pauper, H. exocellata, H. ankova, and H. subsimilis are all humid forest interior specialists. H. narcissus is associated with eastern rainforest edges but also found in a range of different habitats. Earlier work has also shown that Heteropsis butterflies are often infected with the endosymbiont Wolbachia (Linares et al., 2009). We therefore developed a diagnostic to survey populations for this endosymbiont with a view to assessing the impact of infection on the phylogeography of Heteropsis species.
Preliminary studies indicate that both generalist species (H. narcissus, H. ankaratra) failed to show any geographic pattern of genetic structure. In contrast, all forest interior specialist species exhibited significant genetic structure that was either associated with western forest relicts or montane forest refugia. H. subsimilis shows an apparent north-south division at the regional level with the southern group extending across the entire length of eastern contiguous forest. In contrast, H. pauper exhibited clearer signatures of western forest fragmentation. Genetic structure within H. ankova also supports a history of western forest fragmentation. Few haplotypes are shared across sites and the most abundant haplotype is restricted to one fragment. Lastly, H. exocellata also shows very strong regional structure that is divided into three groups: one extended across much of the island, the second is restricted to the contiguous forests of Makira in the North of the island and a third group is restricted to a central forest relict. Future work will examine the timing and pattern of diversification of all species within the genus Heteropsis. This work is being carried out in collaboration with Dr. D. C. Lees at Cambridge University, U.K.
Linares MC, Soto-Calderon ID, Lees DC and Anthony NM (2009) High mitochondrial diversity in geographically widespread butterflies of Madagascar: A test of the DNA barcoding approach Molecular Phylogenetics and Evolution 50: 485-495.
The aim of this study is therefore to test these three major diversity hypotheses using mitochondrial sequence data obtained from multiple populations from each of six species within the butterfly genus Heteropsis that vary in their degree of forest association: H. ankaratra is a grassland generalist that is widely distributed across the island. H. pauper, H. exocellata, H. ankova, and H. subsimilis are all humid forest interior specialists. H. narcissus is associated with eastern rainforest edges but also found in a range of different habitats. Earlier work has also shown that Heteropsis butterflies are often infected with the endosymbiont Wolbachia (Linares et al., 2009). We therefore developed a diagnostic to survey populations for this endosymbiont with a view to assessing the impact of infection on the phylogeography of Heteropsis species.
Preliminary studies indicate that both generalist species (H. narcissus, H. ankaratra) failed to show any geographic pattern of genetic structure. In contrast, all forest interior specialist species exhibited significant genetic structure that was either associated with western forest relicts or montane forest refugia. H. subsimilis shows an apparent north-south division at the regional level with the southern group extending across the entire length of eastern contiguous forest. In contrast, H. pauper exhibited clearer signatures of western forest fragmentation. Genetic structure within H. ankova also supports a history of western forest fragmentation. Few haplotypes are shared across sites and the most abundant haplotype is restricted to one fragment. Lastly, H. exocellata also shows very strong regional structure that is divided into three groups: one extended across much of the island, the second is restricted to the contiguous forests of Makira in the North of the island and a third group is restricted to a central forest relict. Future work will examine the timing and pattern of diversification of all species within the genus Heteropsis. This work is being carried out in collaboration with Dr. D. C. Lees at Cambridge University, U.K.
Linares MC, Soto-Calderon ID, Lees DC and Anthony NM (2009) High mitochondrial diversity in geographically widespread butterflies of Madagascar: A test of the DNA barcoding approach Molecular Phylogenetics and Evolution 50: 485-495.
