Patterns of ecomorphological convergence among mainland and island Anolis lizards

Differing selective pressures on islands versus the mainland may produce alternative evolutionary outcomes among closely related lineages. Conversely, lineages may be constrained to produce similar outcomes in different mainland and island environments, or mainland and island environments may not differ significantly. Among the best‐studied island radiations are Caribbean Anolis lizards. Distinct morphotypes, or ‘ecomorphs’, have been described, and the same ecomorphs have evolved independently on each Greater Antillean island. The mainland Anolis radiation has received much less attention. We use a large morphological data set and a novel phylogenetic hypothesis to show that mainland Anolis did not evolve the same morphotypes as island Anolis, despite some island species being more closely related to mainland species than to island species that share their morphotype. A maximum of four of the six Caribbean ecomorphs were found to exist on the mainland, and just 15 of 123 mainland species are assignable to a Caribbean ecomorph. This result was insensitive to differing taxon samples and alternative phylogenetic hypotheses. Mainland convergence to a Caribbean ecomorph occurs only among species assigned to the grass‐bush ecomorph. Thus, the ecomorphs that have evolved convergently multiple times in the Caribbean have not evolved in parallel on the mainland. These results are consistent with the hypothesis that mainland and island environments offer different selective pressures. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 852–859.     

Phylogeographic and phenotypic outcomes of brown anole colonization across the Caribbean provide insight into the beginning stages of an adaptive radiation

Some of the most important insights into the ecological and evolutionary processes of diversification and speciation have come from studies of island adaptive radiations, yet relatively little research has examined how these radiations initiate. We suggest that Anolis sagrei is a candidate for understanding the origins of the Caribbean Anolis adaptive radiation and how a colonizing anole species begins to undergo allopatric diversification, phenotypic divergence and, potentially, speciation. We undertook a genomic and morphological analysis of representative populations across the entire native range of A. sagrei, finding that the species originated in the early Pliocene, with the deepest divergence occurring between western and eastern Cuba. Lineages from these two regions subsequently colonized the northern Caribbean. We find that at the broadest scale, populations colonizing areas with fewer closely related competitors tend to evolve larger body size and more lamellae on their toepads. This trend follows expectations for post‐colonization divergence from progenitors and convergence in allopatry, whereby populations freed from competition with close relatives evolve towards common morphological and ecological optima. Taken together, our results show a complex history of ancient and recent Cuban diaspora with populations on competitor‐poor islands evolving away from their ancestral Cuban populations regardless of their phylogenetic relationships, thus providing insight into the original diversification of colonist anoles at the beginning of the radiation. Our research also supplies an evolutionary framework for the many studies of this increasingly important species in ecological and evolutionary research.     

Patterns of morphological diversification of mainland Anolis lizards from northwestern South America

Anolis lizards are one of the most diverse vertebrate genera and are the classic example of adaptive radiation and convergent evolution. Anoles exhibit great morphological diversity produced by the ecological opportunity to exploit several arboreal niches. Anole radiation in the Caribbean islands is well studied, but the mainland radiation is less understood. We used a large morphological data set and a molecular phylogeny to describe the morphological diversification of anoles from northwestern South America, a region with the highest anole diversity on a mainland. We describe morphological diversity as summarized by ten morphotypes, defined mainly by body size, limb proportions, and subdigital lamellae. We show that some morphotypes are limited to forested lowlands and others to Andean highlands; by contrast, Anolis assemblages from tropical rainforests are comprised of the same four morphotypes. We demonstrate that morphological diversification followed a pattern of adaptive radiation across a landscape of adaptive peaks. Our results are consistent with the most recent hypothesis of convergence stated for Caribbean radiation, and demonstrate convergence between mainland morphotypes and Caribbean ecomorphs, which suggests that common processes are driving both radiations. © 2016 The Linnean Society of London     

New Species of Closely Related Endosymbiotic Dinoflagellates in the Greater Caribbean have Niches Corresponding to Host Coral Phylogeny

Symbiotic dinoflagellates in the genus Breviolum (formerly Symbiodinium Clade B) dominate coral communities in shallow waters across the Greater Caribbean. While some formally described species exist, mounting genetic, and ecological evidence indicate that numerous more comprise this genus, many of which are closely related. To test this, colonies of common reef‐building corals were sampled across a large geographical range. Phylogenetic and population genetic markers then used to examine evolutionary divergence and delineate boundaries of genetic recombination. Three new candidate species were distinguished by fixed differences in nucleotide sequences from nuclear and chloroplast DNA. Population connectivity was evident within each lineage over thousands of kilometers, however, substantial genetic structure persisted between lineages co‐occurring within sampling locations, signifying reproductive isolation. While geographically widespread with overlapping distributions, each species is ecologically distinct, exhibiting specific mutualisms with phylogenetically distinct coral hosts. Moreover, significant differences in mean cell sizes provide some morphological evidence substantiating formal species distinctions. In providing evidence that satisfies the biological, phylogenetic, ecological, and morphological species concepts, we classify and formally name Breviolum faviinorum n. sp., primarily associated with Caribbean corals belonging to the Caribbean subfamily Faviinae; B. meandrinium n. sp., associated with corals belonging to the family Meandrinidae; and B. dendrogyrum n. sp., a symbiont harbored exclusively by the threatened coral Dendrogyra cylindrus. These findings support the primary importance of niche diversification (i.e. host habitat) in the speciation of symbiotic dinoflagellates.     

Expanding the understanding of local community assembly in adaptive radiations

Communities are thought to be assembled by two types of filters: by the environment relating to the fundamental niche and by biotic interactions relating to the realized niche. Both filters include parameters related to functional traits and their variation along environmental gradients. Here, we infer the general importance of environmental filtering of a functional trait determining local community assembly within insular adaptive radiations on the example of Caribbean Anolis lizards. We constructed maps for the probability of presence of Anolis ecomorphs (ecology‐morphology‐behavior specialists) on the Greater Antilles and overlaid these to estimate ecomorph community completeness (ECC) over the landscape. We then tested for differences in environmental parameter spaces among islands for real and cross‐fitted ECC values to see whether the underlying assembly filters are deterministic (i.e., similar among islands). We then compared information‐theoretic models of climatic and landscape parameters among Greater Antillean islands and inferred whether body mass as functional trait determines ECC. We found areas with high ECC to be strongly correlated with environmental filters, partly related to elevation. The environmental parameters influencing high ECC differed among islands. With the exception of the Jamaican twig ecomorph (which we suspect to be misclassified), smaller ecomorphs were more restricted to higher elevations than larger ones which might reflect filtering on the basis of differential physiological restrictions of ecomorphs. Our results in Anolis show that local community assembly within adaptive island radiations of animals can be determined by environmental filtering of functional traits, independently from species composition and realized environmental niche space.     

Multivariate species boundaries and conservation of harlequin poison frogs

In this study, we present an iterative method for delimiting species under the general lineage concept (GLC) based on the multivariate clustering of morphological, ecological and genetic data. Our rationale is that distinct multivariate groups correspond to evolutionarily independent metapopulation lineages because they reflect the common signal of different secondary defining properties (environmental and genetic distinctiveness, phenotypic diagnosability, etc.) that imply the existence of barriers preventing or limiting gene exchange. We applied this method to study a group of endangered poison frogs, the Oophaga histrionica complex. In our study case, we used next‐generation targeted amplicon sequencing to obtain a robust genetic data set that we combined with patterns of morphological and ecological features. Our analyses revealed the existence of at least five different species in the histrionica complex (three, new to science), some of them, occurring in small isolated populations outside any protected areas. The lineage delimitation proposed here has important conservation implications as it revealed that some of the Oophaga species should be considered among the most vulnerable of the Neotropical frogs. More broadly, our study exemplifies how multiple‐amplicon and multivariate statistical techniques can be integrated to successfully identify species and their boundaries.     

Multilocus phylogeny and a new classification for Southeast Asian and Melanesian forest frogs (family Ceratobatrachidae)

We present a near comprehensive, densely sampled, multilocus phylogenetic estimate of species relationships within the anuran family Ceratobatrachidae, a morphologically and ecologically diverse group of frogs from the island archipelagos of Southeast Asia and the South‐West Pacific. Ceratobatrachid frogs consist of three clades: a small clade of enigmatic, primarily high‐elevation, semi‐aquatic Sundaland species currently assigned to Ingerana (for which we erect a new genus), which is the sister taxon of two large, monophyletic radiations, each situated on islands on either side of Wallace's Line. One radiation is composed of Philippine species of Platymantis and the other contains all taxa from the eastern Indonesian, New Guinean, Solomon, Bismarck, and Fijian archipelagos. Several additional genera (Batrachylodes, Discodeles, Ceratobatrachus, and Palmatorappia) are nested within Platymantis, and of these Batrachylodes and Discodeles are nonmonophyletic. To address the widespread paraphyly of the genus Platymantis and several additional nomenclatural issues, we undertook a wholesale nomenclatural reorganization of the family. Given our partially unresolved phylogeny, and in order to impart a conservative, stable taxonomy, involving a minimal number of genus‐species couplet changes, we propose a conservative classification representing a few compromises. These changes are designed to preserve maximally the presumed original intent of taxonomy (widely used group names associated with morphological and ecological diversity of particular species or groups of species) while implementing a hierarchical system that is consistent with the estimate of phylogeny based on new molecular data. © 2015 The Linnean Society of London     

Convergent evolution of morphology and habitat use in the explosive Hawaiian fancy case caterpillar radiation

Species occurring in unconnected, but similar habitats and under similar selection pressures often display strikingly comparable morphology, behaviour and life history. On island archipelagos where colonizations and extinctions are common, it is often difficult to separate whether similar traits are a result of in situ diversification or independent colonization without a phylogeny. Here, we use one of Hawaii's most ecologically diverse and explosive endemic species radiations, the Hawaiian fancy case caterpillar genus Hyposmocoma, to test whether in situ diversification resulted in convergence. Specifically, we examine whether similar species utilizing similar microhabitats independently developed largely congruent larval case phenotypes in lineages that are in comparable, but isolated environments. Larvae of these moths are found on all Hawaiian Islands and are characterized by an extraordinary array of ecomorphs and larval case morphology. We focus on the ‘purse cases’, a group that is largely specialized for living within rotting wood. Purse cases were considered a monophyletic group, because morphological, behavioural and ecological traits appeared to be shared among all members. We constructed a phylogeny based on nuclear and mitochondrial DNA sequences from 38 Hyposmocoma species, including all 14 purse case species and 24 of non‐purse case congeners. Divergence time estimation suggests that purse case lineages evolved independently within dead wood and developed nearly identical case morphology twice: once on the distant Northwest Hawaiian Islands between 15.5 and 9 Ma and once on the younger main Hawaiian Islands around 3.0 Ma. Multiple ecomorphs are usually found on each island, and the ancestral ecomorph of Hyposmocoma appears to have lived on tree bark. Unlike most endemic Hawaiian radiations that follow a clear stepwise progression of colonization, purse case Hyposmocoma do not follow a pattern of colonization from older to younger island. We postulate that the diversity of microhabitats and selection from parasitism/predation from endemic predators may have shaped case architecture in this extraordinary endemic radiation of Hawaiian insects.     

Evidence for ecological speciation via a host shift in the holly leaf miner,Phytomyza glabricola (Diptera: Agromyzidae)

Evolutionary radiations have been well documented in plants and insects, and natural selection may often underly these radiations. If radiations are adaptive, the diversity of species could be due to ecological speciation in these lineages. Agromyzid flies exhibit patterns of repeated host‐associated radiations. We investigated whether host‐associated population divergence and evidence of divergent selection exist in the leaf miner Phytomyza glabricola on its sympatric host plants, the holly species, Ilex coriacea and I. glabra. Using AFLPs and nuclear sequence data, we found substantial genetic divergence between host‐associated populations of these flies throughout their geographic range. Genome scans using the AFLP data identified 13 loci under divergent selection, consistent with processes of ecological speciation. EF‐1α data suggest that I. glabra is the original host of P. glabricola and that I. coriacea is the novel host, but the AFLP data are ambiguous with regard to directionality of the host shift.     

ACCELERATED EVOLUTION OF LAND SNAILS MANDARINA IN THE OCEANIC BONIN ISLANDS: EVIDENCE FROM MITOCHONDRIAL DNA SEQUENCES

An endemic land snail genus Mandarina of the oceanic Bonin (Ogasawara) Islands shows exceptionally rapid evolution not only of morphological and ecological traits, but of DNA sequence. A phylogenetic relationship based on mitochondrial DNA (mtDNA) sequences suggests that morphological differences equivalent to the differences between families were produced between Mandarina and its ancestor during the Pleistocene. The inferred phylogeny shows that species with similar morphologies and life habitats appeared repeatedly and independently in different lineages and islands at different times. Sequential adaptive radiations occurred in different islands of the Bonin Islands and species occupying arboreal, semiarboreal, and terrestrial habitat arose independently in each island. Because of a close relationship between shell morphology and life habitat, independent evolution of the same life habitat in different islands created species possesing the same shell morphology in different islands and lineages. This rapid evolution produced some incongruences between phylogenetic relationship and species taxonomy. Levels of sequence divergence of mtDNA among the species of Mandarina is extremely high. The maximum level of sequence divergence at 16S and 12S ribosomal RNA sequence within Mandarina are 18.7% and 17.7%, respectively, and this suggests that evolution of mtDNA of Mandarina is extremely rapid, more than 20 times faster than the standard rate in other animals. The present examination reveals that evolution of morphological and ecological traits occurs at extremely high rates in the time of adaptive radiation, especially in fragmented environments.     

Evolution of body shape in differently coloured sympatric congeners and allopatric populations of Lake Malawi's rock‐dwelling cichlids

The cichlid fishes of Lake Malawi represent one of the most diverse adaptive radiations of vertebrates known. Among the rock‐dwelling cichlids (mbuna), closely related sympatric congeners possess similar trophic morphologies (i.e. cranial and jaw structures), defend overlapping or adjacent territories, but can be easily distinguished based on male nuptial coloration. The apparent morphological similarity of congeners, however, leads to an ecological conundrum: theory predicts that ecological competition should lead to competitive exclusion. Hence, we hypothesized that slight, yet significant, ecological differences accompanied the divergence in sexual signals and that the divergence of ecological and sexual traits is correlated. To evaluate this hypothesis, we quantified body shape, a trait of known ecological importance, in populations of Maylandia zebra, a barred, widespread mbuna, and several sympatric nonbarred congeners. We found that the barred populations differ in body shape from their nonbarred sympatric congeners and that the direction of shape differences was consistent across all barred vs. nonbarred comparisons. Barred populations are generally deeper bodied which may be an adaptation to the structurally complex habitat they prefer, whereas the nonbarred species have a more fusiform body shape, which may be adaptive in their more open microhabitat. Furthermore, M. zebra populations sympatric with nonbarred congeners differ from populations where the nonbarred phenotype is absent and occupy less morphospace, indicating potential ecological character displacement. Mitochondrial DNA as well as published AFLP data indicated that the nonbarred populations are not monophyletic and therefore may have evolved multiple times independently. Overall our data suggest that the evolution of coloration and body shape may be coupled as a result of correlational selection. We hypothesize that correlated evolution of sexually selected and ecological traits may have contributed to rapid speciation as well as the maintenance of diversity in one of the most diverse adaptive radiations known.     

Congruent population genetic structure but differing depths of divergence for three alpine stoneflies with similar ecology and geographic distributions

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Dimorphism and divergence in island and mainland Anoles

Relative to the West Indies, the ecology and evolution of anoles inhabiting islands off Central and South America have received little attention. The paucity of studies on continental islands has limited our ability to generalize and extend results based on the West Indian paradigm, as well as our understanding of the profound differences between the adaptive radiations of continental vs. Greater Antillean anoles. Here we compare the morphological, ecological, behavioural and genetic divergence between Anolis nebulosus populations inhabiting a small island in the Bay of Chamela, Mexico, and a nearby mainland forest. Notably, the two populations exhibit intra‐sexual dimorphism with respect to head and limb sizes, the first such polymorphism documented for an Anolis species. We also compare the shape of island and mainland A. nebulosus with each other, the six West Indian ecomorphs and a hypothetical generalist species. Finally, we address the generalist convergence hypothesis for anoles on single species islands. We conclude that convergence on a generalist morphology is widespread among solitary anoles in the West Indies. We present data on a limited sample of solitary anoles with mainland ancestors that suggest a parallel convergence on a similar generalist morphology, probably due to similar adaptive landscapes shaped by selective forces common to small island environments.     

The cryptic origins of evolutionary novelty: 1000‐fold faster trophic diversification rates without increased ecological opportunity or hybrid swarm

Ecological opportunity is frequently proposed as the sole ingredient for adaptive radiation into novel niches. An additional trigger may be genome‐wide hybridization resulting from “hybrid swarm.” However, these hypotheses have been difficult to test due to the rarity of comparable control environments lacking adaptive radiations. Here I exploit such a pattern in microendemic radiations of Caribbean pupfishes. I show that a sympatric three species radiation on San Salvador Island, Bahamas diversified 1445 times faster than neighboring islands in jaw length due to the evolution of a novel scale‐eating adaptive zone from a generalist ancestral niche. I then sampled 22 generalist populations on seven neighboring islands and measured morphological diversity, stomach content diversity, dietary isotopic diversity, genetic diversity, lake/island areas, macroalgae richness, and Caribbean‐wide patterns of gene flow. None of these standard metrics of ecological opportunity or gene flow were associated with adaptive radiation, except for slight increases in macroalgae richness. Thus, exceptional trophic diversification is highly localized despite myriad generalist populations in comparable environmental and genetic backgrounds. This study provides a strong counterexample to the ecological and hybrid swarm theories of adaptive radiation and suggests that diversification of novel specialists on a sparse fitness landscape is constrained by more than ecological opportunity and gene flow.     

AN ADAPTIVE RADIATION OF FROGS IN A SOUTHEAST ASIAN ISLAND ARCHIPELAGO

Living amphibians exhibit a diversity of ecologies, life histories, and species‐rich lineages that offers opportunities for studies of adaptive radiation. We characterize a diverse clade of frogs (Kaloula, Microhylidae) in the Philippine island archipelago as an example of an adaptive radiation into three primary habitat specialists or ecotypes. We use a novel phylogenetic estimate for this clade to evaluate the tempo of lineage accumulation and morphological diversification. Because species‐level phylogenetic estimates for Philippine Kaloula are lacking, we employ dense population sampling to determine the appropriate evolutionary lineages for diversification analyses. We explicitly take phylogenetic uncertainty into account when calculating diversification and disparification statistics and fitting models of diversification. Following dispersal to the Philippines from Southeast Asia, Kaloula radiated rapidly into several well‐supported clades. Morphological variation within Kaloula is partly explained by ecotype and accumulated at high levels during this radiation, including within ecotypes. We pinpoint an axis of morphospace related directly to climbing and digging behaviors and find patterns of phenotypic evolution suggestive of ecological opportunity with partitioning into distinct habitat specialists. We conclude by discussing the components of phenotypic diversity that are likely important in amphibian adaptive radiations.     

Dispersal barriers and climate determine the geographic distribution of the helicopter damselfly Mecistogaster modesta

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Lack of convergence in aquatic Anolis lizards

Why convergent evolution occurs among some species occupying similar habitats but not among others is a question that has received surprisingly little attention. Caribbean Anolis lizards, known for their extensive convergent evolution among islands in the Greater Antilles, are an appropriate group with which to address this question. Despite the well-documented pattern of between-island convergence, some Greater Antillean anoles are not obviously part of the convergence syndrome. One example involves aquatic anoles--species that are found near to and readily enter streams-which have evolved independently twice in the Caribbean and also twice on mainland Central America. Despite being found in similar habitats, no previous study has investigated whether aquatic anoles represent yet another case of morphological convergence. We tested this hypothesis by collecting morphological data for seven aquatic anole species and 29 species from the six convergent types of Greater Antillean habitat specialists. We failed to find evidence for morphological convergence: the two Caribbean aquatic species are greatly dissimilar to each other and to the Central American species, which, however, may be convergent upon each other. We suggest two possible reasons for this lack of convergence in an otherwise highly convergent system: either there is more than one habitat type occupied by anoles in the proximity of water, or there is more than one way to adapt to a single aquatic habitat. We estimate that almost all of the 113 species of Greater Antillean anoles occupy habitats that are also used by distantly related species, but only 15% of these species are not morphologically similar to their distantly related ecological counterparts. Comparative data from other taxa would help enlighten the question of why the extent of convergence is so great in some lineages and not in others.     

CRATER LAKE HABITAT PREDICTS MORPHOLOGICAL DIVERSITY IN ADAPTIVE RADIATIONS OF CICHLID FISHES

Adaptive radiations provide an excellent opportunity for studying the correlates and causes for the origin of biodiversity. In these radiations, species diversity may be influenced by either the ecological and physical environment, intrinsic lineage effects, or both. Disentangling the relative contributions of these factors in generating biodiversity remains a major challenge in understanding why a lineage does or does not radiate. Here, we examined morphological variation in body shape for replicate flocks of Nicaraguan Midas cichlid fishes and tested its association with biological and physical characteristics of their crater lakes. We found that variability of body elongation, an adaptive trait in freshwater fishes, is mainly predicted by average lake depth (N = 6, P < 0.001, R² = 0.96). Other factors considered, including lake age, surface area, littoral zone area, number of co‐occurring fish species, and genetic diversity of the Midas flock, did not significantly predict morphological variability. We also showed that lakes with a larger littoral zone have on average higher bodied Midas cichlids, indicating that Midas cichlid flocks are locally adapted to their crater lake habitats. In conclusion, we found that a lake's habitat predicts the magnitude and the diversity of body elongation in repeated cichlid adaptive radiations.     

Integrated species delimitation and conservation implications of an endangered weevil Pachyrhynchus sonani (Coleoptera: Curculionidae) in Green and Orchid Islands of Taiwan

Oceanic islands are productive habitats for generating new species and high endemism, which is primarily due to their geographical isolation, smaller population sizes and local adaptation. However, the short divergence times and subtle morphological or ecological divergence of insular organisms may obscure species identity, so the cryptic endemism on islands may be underestimated. The endangered weevil Pachyrhynchus sonani Kôno (Coleoptera: Curculionidae: Entiminae: Pachyrhynchini) is endemic to Green Island and Orchid Island of the Taiwan‐Luzon Archipelago and displays widespread variation in coloration and host range, thus raising questions regarding its species boundaries and degree of cryptic diversity. We tested the species boundaries of P. sonani using an integrated approach that combined morphological (body size and shape, genital shape, coloration and cuticular scale), genetic (four genes and restriction site‐associated DNA sequencing, RAD‐seq) and ecological (host range and distribution) diversity. The results indicated that all the morphological datasets for male P. sonani, except for the colour spectrum, reveal overlapping but statistically significant differences between islands. In contrast, the morphology of the female P. sonani showed minimum divergence between island populations. The populations of P. sonani on the two islands were significantly different in their host ranges, and the genetic clustering and phylogenies of P. sonani established two valid evolutionary species. Integrated species delimitation combining morphological, molecular and ecological characters supported two distinct species of P. sonani from Green Island and Orchid Island. The Green Island population was described as P. jitanasaius sp.n. Chen & Lin, and it is recommended that its threatened conservation status be recognized. Our findings suggest that the inter‐island speciation of endemic organisms inhabiting both islands may be more common than previously thought, and they highlight the possibility that the cryptic diversity of small oceanic islands may still be largely underestimated.     

Behavioural tactics used by invasive cane toads (Rhinella marina) to exploit apiaries in Australia

Behavioural flexibility plays a key role in facilitating the ability of invasive species to exploit anthropogenically‐created resources. In Australia, invasive cane toads (Rhinella marina) often gather around commercial beehives (apiaries), whereas native frogs do not. To document how toads use this resource, we spool‐tracked cane toads in areas containing beehives and in adjacent natural habitat without beehives, conducted standardized observations of toad feeding behaviour, and ran prey‐manipulation trials to compare the responses of cane toads versus native frogs to honeybees as potential prey. Toads feeding around beehives travelled shorter distances per night, and hence used different microhabitats, than did toads from nearby control sites without beehives. The toads consumed live bees from the hive entrance (rather than dead bees from the ground), often climbing on top of one another to gain access to the hive entrance. Prey manipulation trials confirm that bee movement is the critical stimulus that elicits the toads’ feeding response; and in standardized trials, native frogs consumed bees less frequently than did toads. In summary, cane toads flexibly modify their movements, foraging behaviour and dietary composition to exploit the nutritional opportunities created by commercial beehives, whereas native anurans do not.