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...

Theory predicts that sexual behaviour in animals can evolve rapidly, accelerating the rate of species formation. Here we estimate the rate of speciation in Laupala, a group of forest-dwelling Hawaiian crickets that is characterized primarily through differences in male courtship song. We find that Laupala has the highest rate of speciation so far recorded in arthropods, supporting the idea that divergence in courtship or sexual behaviour drives rapid speciation in animals.

We introduce a statistic, the genealogical sorting index (gsi), for quantifying the degree of exclusive ancestry of labeled groups on a rooted genealogy and demonstrate its application. The statistic is simple, intuitive, and easily calculated. It has a normalized range to facilitate comparisons among different groups, trees, or studies and it provides information on individual groups rather than a composite measure for all groups. It naturally handles polytomies and accommodates measures of uncertainty in phylogenetic relationships. We use coalescent simulations to explore the behavior of the gsi across a range of divergence times, with the mean value increasing to 1, the maximum value when exclusivity within a group reached monophyly. Simulations also demonstrate that the power to reject the null hypothesis of mixed genealogical ancestry increased markedly as sample size increased, and that the gsi provides a statistically more powerful measure of divergence than F ST . Applications to data from published studies demonstrated that the gsi provides a useful way to detect significant exclusivity even when groups are not monophyletic. Although we describe this statistic in the context of divergence, it is more broadly applicable to quantify and assess the significance of clustering of observations in labeled groups on any tree.

Eukaryotic genome sizes range over five orders of magnitude. This variation cannot be explained by differences in organismic complexity (the C value paradox). To test the hypothesis that some variation in genome size can be attributed to differences in the patterns of insertion and deletion (indel) mutations among organisms, this study examines the indel spectrum in Laupala crickets, which have a genome size 11 times larger than that of Drosophila. Consistent with the hypothesis, DNA loss is more than 40 times slower in Laupala than in Drosophila.

The natural habitats of many species have become fragmented into small "islands," principally by human activities. In this paper we discuss the long-term genetic and evolutionary consequences of fragmentation as inferred from studies on populations that have undergone natural habitat fragmentation in the Ozark Mountains. The Ozarks are the highest land formation found in the midwestern United States. Because of the absence of major geographical barriers around the Ozarks, plants and animals from diverse parts of the continent have been able to invade the area during post-Pleistocene climatic periods. Many of these invasions were short-lived, but the geological and topographical complexity of the Ozarks provided numerous relictual habitats. As a

Adaptive radiation plays a fundamental role in our understanding of the evolutionary process. However, the concept has provoked strong and differing opinions concerning its definition and nature among researchers studying a wide diversity of systems. Here, we take a broad view of what constitutes an adaptive radiation, and seek to find commonalities among disparate examples, ranging from plants to invertebrate and vertebrate animals, and remote islands to lakes and continents, to better understand processes shared across adaptive radiations. We surveyed many groups to evaluate factors considered important in a large variety of species radiations. In each of these studies, ecological opportunity of some form is identified as a prerequisite for adaptive radiation. However, evolvability, which can be enhanced by hybridization between distantly related species, may play a role in seeding entire radiations. Within radiations, the processes that lead to speciation depend largely on (1) whether the primary drivers of ecological shifts are (a) external to the membership of the radiation itself (mostly divergent or disruptive ecological selection) or (b) due to competition within the radiation membership (interactions among members) subsequent to reproductive isolation in similar environments, and (2) the extent and timing of admixture. These differences translate into different patterns of species accumulation and subsequent patterns of diversity across an adaptive radiation. Adaptive radiations occur in an extraordinary diversity of different ways, and continue to provide rich data for a better understanding of the diversification of life.

Remote island archipelagos offer superb opportunities to study the evolution of community assembly because of their relatively young and simple communities where speciation contributes to the origin and evolution of community structure. There is great potential for common phylogeographic patterns among remote archipelagos that originate through hotspot volcanism, particularly when the islands formed are spatially isolated and linearly arranged. The progression rule is characterized by a phylogeographic concordance between island age and lineage age in a species radiation. Progression is most likely to arise when a species radiation begins on an older island before the emergence of younger islands of a hotspot archipelago. In the simplest form of progression, colonization of younger islands as they emerge and offer appropriate habitat, is coincident with cladogenesis. In this paper, we review recent discoveries of the progression rule on seven hotspot archipelagos. We then discuss advantages that progression offers to the study of community assembly, and insights that community dynamics may offer toward understanding the evolution of progression. We describe results from two compelling cases of progression where the mosaic genome may offer insights into contrasting demographic histories that shed light on mechanisms of speciation and progression on remote archipelagos.progression rule | speciation | priority effect | community assembly | radiation zone

Female preference functions for di¡erent sexual traits can di¡er signi¢cantly, from`unimodal' to`open ended'. Through the study of acoustic communication in anurans, several studies have reported an association between static (stereotyped) traits versus dynamic (variable) traits and preference function shape (unimodal versus open ended, respectively). Observing a similar pattern in a phylogenetically independent group would suggest that deterministic forces have caused a relationship between signal variability and preference function shape in acoustic signalling systems. We examined this phenomenon in crickets, another animal characterized by intersexual acoustic communication. We measured the withinmale variability for three acoustic features of the male calling song in Laupala cerasina and the corresponding shape of the female preference function for each of these features. We o¡er support for the generalization that open-ended preference functions correspond to relatively dynamic courtship traits and unimodal preference functions correspond to relatively static courtship traits. We discuss the evolutionary signi¢cance of these ¢ndings in the context of the natural history of the Laupala species radiation.