Espécies crípticas em Pagamea coriacea sensu lato (Rubiaceae): evidências morfológicas, ecológicas e de comportamento reprodutivo em um contexto simpátrico

In this study we explore morphological and ecological variation in sympatric populations of Pagamea coriacea s.l. - a species complex from white-sand vegetation in the Amazon. A total of 147 trees were sampled and monitored at three nearby sites in Central Amazon, Brazil. Multivariate analyses of morphology indicated two distinct groups (A and B), which also differed in bark type, each containing subgroups associated with sexual dimorphism. However, a single hermaphroditic individual was observed within group B. As expected, all pistillate plants produced fruits, but 23% of the staminate plants of group B, and 5% of group A also produced fruits. This variation suggests that the sexual systems of both groups are between dioecy and gynodioecy. There was an overlap in flowering phases between the two groups, but the pattern of floral maturation differed. Ecologically, plants of group B were found in more shaded habitats and over sandstone bedrocks, while group A was prevalent in deeper sandy soils as canopy plants. The significances of morphological and environmental differences were tested by a multivariate analysis of variance, and a canonical discriminant analysis assessed the importance of variables. The coexistence in sympatry of two discrete morphological groups in the P. coriacea s.l., with different habitat preferences and reproductive behaviors, indicates they represent distinct species.O objetivo deste estudo foi testar se o complexo de espécies Pagamea coriacea inclui múltiplas espécies, usando evidências morfológicas, ecológicas e de comportamento reprodutivo. Um total de 147 árvores foram amostradas e monitoradas em três locais próximos na Amazônia Central, Brasil. Análises multivariadas de dados morfológicos indicaram dois grupos discretos (A e B), que coincidem com diferenças no tipo de casca, cada um por sua vez com subgrupos que representam dimorfismo sexual. Contudo, um indivíduo distintamente hermafrodita foi encontrado no grupo B. Todas as plantas pistiladas produziram frutos, mas também foram observados frutos para 23% das plantas estaminadas do grupo B, e para 5% das estaminadas do grupo A. Essa variação sugere que ambos grupos possuem um sistema sexual entre dioicia e ginodioicia. Houve sobreposição das fases de floração e frutificação entre os dois grupos, mas o padrão de maturação de flores foi diferente. Quanto ao hábitat, o grupo B predominou em situações de sombra e em solos arenosos rasos sobre lajes de pedra, enquanto o grupo A ocorreu em solos arenosos mais profundos e no dossel da vegetação. A coexistência de dois grupos morfológicos discretos no complexo P. coriacea s.l., com diferenças ecológicas e de comportamento reprodutivo, indica que correspondem a duas espécies distintas

Testing species boundaries in an ancient species complex with deep phylogeographic history: Genus Xantusia(Squamata: Xantusiidae)

Identification of species in natural populations has recently received increased attention with a number of investigators proposing rigorous methods for species delimitation. Morphologically conservative species (or species complexes) with deep phylogenetic histories (and limited gene flow) are likely to pose particular problems when attempting to delimit species, yet this is crucial to comparative studies of the geography of speciation. We apply two methods of species delimitation to an ancient group of lizards (genus Xantusia) that occur throughout southwestern North America. Mitochondrial cytochrome b and nicotinamide adenine dinucleotide dehydrogenase subunit 4 gene sequences were generated from samples taken throughout the geographic range of Xantusia. Maximum likelihood, Bayesian, and nested cladogram analyses were used to estimate relationships among haplotypes and to infer evolutionary processes. We found multiple well-supported independent lineages within Xantusia, for which there is considerable discordance with the currently recognized taxonomy. High levels of sequence divergence (21.3%) suggest that the pattern in Xantusia may predate the vicariant events usually hypothesized for the fauna of the Baja California peninsula, and the existence of deeply divergent clades (18.8%-26.9%) elsewhere in the complex indicates the occurrence of ancient sundering events whose genetic signatures were not erased by the late Wisconsin vegetation changes. We present a revised taxonomic arrangement for this genus consistent with the distinct mtDNA lineages and discuss the phylogeographic history of this genus as a model system for studies of speciation in North American deserts