Conflict between nuclear and mitochondrial DNA phylogenies of a recent species radiation: What mtDNA reveals and conceals about modes of speciation in Hawaiian crickets

Abstract

It has been asserted that recent mtDNA phylogenies support the plausibility of sympatric speciation, long considered a controversial mechanism of the origin of species. If such inferences are reliable, mtDNA phylogenies should be congruent with phylogenies based on other data. In previous work, a mtDNA phylogeny suggested that diversification of the Hawaiian cricket genus Laupala was initiated by single invasions into each of several Hawaiian islands, followed by multiple sympatric divergences within each island. In contrast, a systematic hypothesis based on morphology argues that speciation in Laupala has occurred primarily in allopatry, with two independent species radiations diversifying across the archipelago. In this study, I analyze nuclear DNA (nDNA) sequences from Laupala to compare with sequences from the mtDNA. The nDNA phylogeny corroborates the hypothesis of allopatric divergence and multiple invasions, and when compared with mtDNA patterns, suggests that interspecific hybridization is a persistent feature of the history of Laupala. The discrepancy between mtDNA and nDNA phylogenies reveals that speciation histories based on mtDNA alone can be extensively misleading.I solated biotas, such as those in island archipelagos or lake habitats, often harbor many complexes of closely related, endemic species coexisting in sympatry. Mayr (1), the wellknown proponent of ''allopatric'' speciation, argued that such biotas are likely the consequence of multiple invasions. Under a multiple-invasions model, closely related species originate in allopatry and come to occupy a common area secondarily by parallel, independent invasions. A single-invasion model, controversial because it requires primary divergence and speciation in sympatry, offers an alternative to the multiple-invasions scenario. Under this alternative, a single invasion by an exclusive common ancestor and in situ divergence leads to the coexistence of two sister species. As Mayr (1) noted, limited levels of morphological or behavioral variation often exist among closely related ''island'' species and their putative source populations, thwarting efforts to estimate the phylogenetic relationships necessary to test these alternatives. Recently, mtDNA genes have been found to vary considerably among closely related species, making phylogenetic estimates of recent species radiations possible.The native rainforests of the Hawaiian archipelago harbor numerous cases of closely related species coexisting in sympatry (2-6). The endemic genus Laupala Otte (2) is part of a large radiation of Ͼ150 flightless species of swordtail crickets (subfamily Trigonidiinae), one of the many native Hawaiian species flocks. The 37 morphologically cryptic species of Laupala are each single-island endemics restricted to the rainforested slopes of the high islands of the Hawaiian archipelago, often living in sympatric communities with one to three acoustically distinct congeners (2, 3, 7). Laupala offers an ideal opportunity to test the likelihood of a multiple-versus single-inv...

Habitat selection and ecological speciation in Galápagos warbler finches ( Certhidea olivacea and Certhidea fusca )

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The biogeography of mitochondrial and nuclear discordance in animals

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