Rate of lineage origin explains the diversity anomaly in the World’s mangrove vegetation

The contribution of nonecological factors to global patterns in diversity is evident when species richness differs between regions with similar habitats and geographic area. Mangrove environments in the Eastern Hemisphere harbor six times as many species of trees and shrubs as similar environments in the New World. Genetic divergence of mangrove lineages from terrestrial relatives, in combination with fossil evidence, suggests that mangrove diversity is limited by evolutionary transition into the stressful marine environment, the number of mangrove lineages has increased steadily over the Tertiary with little global extinction, and the diversity anomaly in mangrove vegetation reflects regional differences in the rate of origin of new mangrove lineages

The dynamic evolutionary history of the bananaquit (Coereba flaveola) in the Caribbean revealed by a multigene analysis

<p>Abstract</p> <p>Background</p> <p>The bananaquit (<it>Coereba flaveola</it>) is a small nectivorous and frugivorous emberizine bird (order Passeriformes) that is an abundant resident throughout the Caribbean region. We used multi-gene analyses to investigate the evolutionary history of this species throughout its distribution in the West Indies and in South and Middle America. We sequenced six mitochondrial genes (3744 base pairs) and three nuclear genes (2049 base pairs) for forty-four bananaquits and three outgroup species. We infer the ancestral area of the present-day bananaquit populations, report on the species' phylogenetic, biogeographic and evolutionary history, and propose scenarios for its diversification and range expansion.</p> <p>Results</p> <p>Phylogenetic concordance between mitochondrial and nuclear genes at the base of the bananaquit phylogeny supported a West Indian origin for continental populations. Multi-gene analysis showing genetic remnants of successive colonization events in the Lesser Antilles reinforced earlier research demonstrating that bananaquits alternate periods of invasiveness and colonization with biogeographic quiescence. Although nuclear genes provided insufficient information at the tips of the tree to further evaluate relationships of closely allied but strongly supported mitochondrial DNA clades, the discrepancy between mitochondrial and nuclear data in the population of Dominican Republic suggested that the mitochondrial genome was recently acquired by introgression from Jamaica.</p> <p>Conclusion</p> <p>This study represents one of the most complete phylogeographic analyses of its kind and reveals three patterns that are not commonly appreciated in birds: (1) island to mainland colonization, (2) multiple expansion phases, and (3) mitochondrial genome replacement. The detail revealed by this analysis will guide evolutionary analyses of populations in archipelagos such as the West Indies, which include islands varying in size, age, and geological history. Our results suggest that multi-gene phylogenies will permit improved comparative analysis of the evolutionary histories of different lineages in the same geographical setting, which provide replicated "natural experiments" for testing evolutionary hypotheses.</p

Postglacial migration supplements climate in determining plant species ranges in Europe

The influence of dispersal limitation on species ranges remains controversial. Considering the dramatic impacts of the last glaciation in Europe, species might not have tracked climate changes through time and, as a consequence, their present-day ranges might be in disequilibrium with current climate. For 1016 European plant species, we assessed the relative importance of current climate and limited postglacial migration in determining species ranges using regression modelling and explanatory variables representing climate, and a novel species-specific hind-casting-based measure of accessibility to postglacial colonization. Climate was important for all species, while postglacial colonization also constrained the ranges of more than 50 per cent of the species. On average, climate explained five times more variation in species ranges than accessibility, but accessibility was the strongest determinant for one-sixth of the species. Accessibility was particularly important for species with limited long-distance dispersal ability, with southern glacial ranges, seed plants compared with ferns, and small-range species in southern Europe. In addition, accessibility explained one-third of the variation in species' disequilibrium with climate as measured by the realized/potential range size ratio computed with niche modelling. In conclusion, we show that although climate is the dominant broad-scale determinant of European plant species ranges, constrained dispersal plays an important supplementary role

Growth rate and maturation of skeletal muscles over a size range of galliform birds

The relationship between growth rate and development of function in leg and pectoral muscles was studied in four species of galliform birds ranging from 125 g to 18 kg and, for comparison, in an altricial species, the European starling (80 g). An index to neonatal maturity (muscle dry content proportion as a fraction of adult value) was higher in leg than in pectoral muscles and lower in larger than in smaller galliforms. The maturity index was substantially lower in starling neonates, After the first week posthatch, however, the maturity index was highest in larger species. Exponential growth rates decreased linearly with increasing maturity in both pectoral and leg muscles, following similar regressions in all species including the starling. At a particular value of the maturity index, the exponential growth rate was higher in pectoral than in leg muscles, The exponential growth rates of muscles of neonatal large galliforms were lower than expected from their low maturity. This may represent the down-regulation shortly after hatching of the high exponential growth rate needed to reach a large hatching mass in a short incubation period. A slower growth rate immediately posthatch may be necessary if the relatively immature neonatal digestive system cannot deliver nutrients or metabolized energy required for more rapid growth. Smaller species may not be faced with the constraint of rapid growth toward the end of the embryonic period

Distributions of Exotic Plants in Eastern Asia and North America

Although some plant traits have been linked to invasion success, the possible effects of regional factors, such as diversity, habitat suitability, and human activity are not well understood. Each of these mechanisms predicts a different pattern of distribution at the regional scale. Thus, where climate and soils are similar, predictions based on regional hypotheses for invasion success can be tested by comparisons of distributions in the source and receiving regions. Here, we analyse the native and alien geographic ranges of all 1567 plant species that have been introduced between eastern Asia and North America or have been introduced to both regions from elsewhere. The results reveal correlations between the spread of exotics and both the native species richness and transportation networks of recipient regions. This suggests that both species interactions and human-aided dispersal influence exotic distributions, although further work on the relative importance of these processes is needed

The relationship between basal metabolic rate and daily energy expenditure in birds and mammals

We examined the relationship between daily energy expenditure (DEE) and basal metabolic rate (BMR) in birds and mammals. Two models of the relationship between DEE and BMR were distinguished: a ''shared pathways'' model in which DEE replaces BMR in the active organism and a ''partitioned pathways'' model in which DEE includes BMR-that is, BMR is separate from the metabolic pathways that result in activity metabolism (ACT), and DEE = ACT + BMR. The appropriate null hypotheses for the relationship between basal and active metabolism are r(DEE . BMR) = 0 and r(ACT . BMR) = 0, respectively. Correlations of the residuals (d and b) of the logarithms of DEE and BMR from their allometric regressions with the logarithm of body mass were tested against these null models. Using phylogenetically independent contrasts, we found no significant relationship between DEE and BMR in birds, but a strong relationship (r(db) = 0.86) among mammals. Thus, the hypothesis that sustained working capacity is related to basal metabolism is supported for mammals but not for birds. Residuals of metabolic variables from allometric regressions on body mass were greater for mammals than for birds and suggest that mammals are more diversified in their energetic physiology. The idea that sustainable energy expenditure may be pushed to physiological limits in mammals but not in birds is not supported, however, because the ratio of DEE to BMR has a somewhat lower mean and greater variance in mammals compared to birds. The nature of the relationship between DEE and BMR in mammals and the apparent absence of such a relationship in birds remain major puzzles in animal physiology

The region effect on mesoscale plant species richness between eastern Asia and eastern North America

The greater number of plant species in temperate eastern Asia compared to eastern North America has been ascribed to both local environment and regional characteristics, but the relative contributions of each have not been resolved. In this analysis, we related species richness of flowering plants in mesoscale floras ( B/10 4 km 2 ) dominated by temperate forest vegetation to area, elevation, latitude, and several climate variables. When analyses were conducted separately within each region, area and, in eastern Asia, elevation, were the primary determinants of species richness. It appears that the number of species in mesic temperate floras within these regions is largely unrelated to the relatively narrow range of local climate factors associated with these floras. Analysis of covariance of the logarithm of species richness with the logarithm of area (b 0/0.148) and climate measurements as independent variables revealed a region effect, with species richness in eastern Asia exceeding that in eastern North America by 0.294 log 10 units, or a factor of 2.0. Similar regional differences in species richness were apparent in floras compiled from larger areas. Understanding differences in plant species richness between regions requires consideration of regional influences, whose effects should be tested in comparative analyses based on floristic surveys of ecologically characterized small areas. R. E. Ricklefs, ([email protected])