ABSTRACT
Extremely high levels of plant diversity in the American tropics are derived from multiple interactions between biotic and abiotic factors. Previous studies have focused on macro-evolutionary dynamics of the Tropical Andes, Amazonia, and Brazil's Cerrado and Atlantic forests during the last decade. Yet, other equally important Neotropical biodiversity hotspots have been severely neglected. This is particularly true for the Chocó region on the north-western coast of South and Central America. This geologically complex region is Earth's ninth most biodiverse hotspot, hosting approximately 3% of all known plant species. Here, we test Gentry's [1982a,b] hypothesis of a northern Andean-Central American Pleistocene origin of the Chocoan flora using phylogenetic reconstructions of representative plant lineages in the American tropics. We show that plant diversity in the Chocó is derived mostly from Andean immigrants. Contributions from more distant biogeographical areas also exist but are fewer. We also identify a strong floristic connection between the Chocó and Central America, revealed by multiple migrations into the Chocó during the last 5 Ma. The dated phylogenetic reconstructions suggest a Plio-Pleistocene onset of the extant Chocó flora. Taken together, these results support to a limited extend Gentry's hypothesis of a Pleistocene origin and of a compound assembly of the Chocoan biodiversity hotspot. Strong Central American-Chocoan floristic affinity may be partly explained by the accretion of a land mass derived from the Caribbean plate to north-western South America. Additional densely sampled phylogenies of Chocoan lineages also well represented across the Neotropics could enlighten the role of land mass movements through time in the assembly of floras in Neotropical biodiversity hotspots.
ABSTRACT
Climate adaptation has major consequences in the evolution and ecology of all living organisms. Though phytophagous insects are an important component of Earth's biodiversity, there are few studies investigating the evolution of their climatic preferences. This lack of research is probably because their evolutionary ecology is thought to be primarily driven by their interactions with their host plants. Here, we use a robust phylogenetic framework and species-level distribution data for the conifer-feeding aphid genus Cinara to investigate the role of climatic adaptation in the diversity and distribution patterns of these host-specialized insects. Insect climate niches were reconstructed at a macroevolutionary scale, highlighting that climate niche tolerance is evolutionarily labile, with closely related species exhibiting strong climatic disparities. This result may suggest repeated climate niche differentiation during the evolutionary diversification of Cinara. Alternatively, it may merely reflect the use of host plants that occur in disparate climatic zones, and thus, in reality the aphid species' fundamental climate niches may actually be similar but broad. Comparisons of the aphids' current climate niches with those of their hosts show that most Cinara species occupy the full range of the climatic tolerance exhibited by their set of host plants, corroborating the hypothesis that the observed disparity in Cinara species' climate niches can simply mirror that of their hosts. However, 29% of the studied species only occupy a subset of their hosts' climatic zone, suggesting that some aphid species do indeed have their own climatic limitations. Our results suggest that in host-specialized phytophagous insects, host associations cannot always adequately describe insect niches and abiotic factors must be taken into account.
ABSTRACT
Various scholars have pioneered sex assessment from different parts of the skeleton based on metrical or qualitative morphological characteristics. Lately though, a new technique which combines both traditional methods is becoming popular in forensic anthropology. Geometric-morphometrics is a field of multivariate statistical biometric analysis which allows the quantification of the shape and size components of morphological variation. The purpose of this investigation is to assess sex from the humerus in a contemporary Greek population using geometric-morphometric analysis of shape data derived from digital radiographs. The study population consists of 97 well-preserved adult humeri from two cemeteries of Heraklion, Crete. The left humeri are radiographed using digital radiograph machine (TCA 4R PLUS). Assuming fragmentary patterns, the proximal and distal ends are studied separately. Five landmarks are selected on the radiograph of the proximal epiphysis and seven landmarks on the distal. Generalised Procrustes analysis (GPA) and thin-plate splines are used to obtain the shape and size variables for statistical analysis. Then three discriminant function analyses were carried out: one uses the PC scores from Procrustes shape space, the second the centroid size alone and the third the PC scores of GPA residuals plus lnCS for analysis in Procrustes form space. Results indicate the existence of shape differences between the sexes. In females the greater tubercle is smoother, with its superior border less pronounced. Additionally, females have a relatively squared distal epiphysis, while males exhibit a more rectangular shape. Shape differences between genders, for the cross-validated data, give slightly better classification results in the proximal humerus (73%) compared with the distal humerus (71%). Size alone performed better (86.5% for proximal and 85.6% for distal humerus). As anticipated, the classification accuracy improves (89.6% for proximal and 89.7% for distal epiphysis) when both size and shape are combined. From the forensic standpoint, the usefulness of this study rests on the identification of sex based on shape differences observed on radiographs of fragmentary humeri that could not be assessed with traditional methods. The analysis of humeral radiographs by geometric-morphometric techniques offers an alternative way to identify the sex of unknown skeletal remains. Whether this is statistically better than simply using traditional osteometric methods is a question that needs to be tested in a meta-statistical approach.
