![]() The patterns evident in the mtDNA phylogeny support a single-invasion model of speciation. Furthermore, in many instances the mtDNA sequences suggest that sympatric species pairs representing Otte's different species groups frequently were each other's closest relatives ( 3, 9), revealing patterns consistent with sympatric speciation. Instead, the mtDNA phylogeny suggests a single, older-to-younger biogeographical species radiation across the Hawaiian archipelago coincident with the chronological age of island formation ( 3). In contrast, phylogenetic relationships inferred from the mtDNA sequences of the three hypothesized species groups ( 3) contradict Otte's ( 2) hypothesized relationships. Therefore, sympatric Laupala communities must have been established by multiple invasions (Fig. Otte ( 2, 8) suggested that each species group shares exclusive common ancestry on the basis of slight metric differences of the male genitalia. Otte ( 2, 8) hypothesized that there are three species groups of Laupala (the kauai, pacifica, and cerasina groups) and that sympatric communities from Oahu, Maui, and Hawaii each have representatives from two of these groups ( pacifica and cerasina). Recently, mtDNA genes have been found to vary considerably among closely related species, making phylogenetic estimates of recent species radiations possible. ![]() 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. Under this alternative, a single invasion by an exclusive common ancestor and in situ divergence leads to the coexistence of two sister species. A single-invasion model, controversial because it requires primary divergence and speciation in sympatry, offers an alternative to the multiple-invasions scenario. Under a multiple-invasions model, closely related species originate in allopatry and come to occupy a common area secondarily by parallel, independent invasions. Mayr ( 1), the well-known proponent of “allopatric” speciation, argued that such biotas are likely the consequence of multiple invasions. Isolated biotas, such as those in island archipelagos or lake habitats, often harbor many complexes of closely related, endemic species coexisting in sympatry. The discrepancy between mtDNA and nDNA phylogenies reveals that speciation histories based on mtDNA alone can be extensively misleading. 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. In this study, I analyze nuclear DNA (nDNA) sequences from Laupala to compare with sequences from the mtDNA. 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 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. If such inferences are reliable, mtDNA phylogenies should be congruent with phylogenies based on other data. ![]() It has been asserted that recent mtDNA phylogenies support the plausibility of sympatric speciation, long considered a controversial mechanism of the origin of species. ![]()
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