Evolution and history of hummingbirds (Aves: Trochilidae) from the Juan Fernandez Islands, Chile

The Juan Fernandez Firecrown Sephanoides fernandensis is an endangered endemic hummingbird that inhabits the Juan Fernandez Islands, 667 km off the coast of Chile. Its population has decreased from several thousand in the early part of this century to approximately 250–400 individuals at present. The reasons for its decline include habitat degradation by anthropogenic forest clearance and the introduction of grazing mammals and rodents. Another hummingbird, the Green-backed Firecrown Sephanoides sephaniodes, inhabits the Juan Fernandez Islands but is also found on the Chilean mainland. It currently numbers several thousand on the Juan Fernandez Islands but was considered rare during the late 19th and early 20th centuries. The sister relationship between the two species has not been critically tested, and so their evolutionary histories on the Juan Fernandez Islands remain uncertain. With the use of mtDNA cytochrome b and ND2 phylogenetic reconstructions, our study supports the two species as sister taxa. Moreover, the molecular data suggest that the genus Sephanoides is closely related to the higher altitude Andean hummingbirds typical of the paramo and puna habitats. The molecular divergence between the two species of Sephanoides indicates they may have become isolated from each other less than 1 million years ago, suggesting that S. fernandensis evolved in situ on the Juan Fernandez Islands. We find no evidence of genetic subdivision between populations of S. sephaniodes from the Juan Fernandez Islands and the mainland. In addition, high genetic variation of the Juan Fernandez Islands population does not indicate a long period of isolation of a limited number of S. sephaniodes but instead suggests a recent colonization event, perhaps from several mainland populations. As a result of molecular, morphological and apparent ecological similarities, we suggest that competition by S. sephaniodes may be an additional factor stifling the recovery of S. fernandensis. Possible conservation strategies include habitat restoration and the removal of introduced mammals; immediate implementation of such conservation management plans are necessary to save this species from extinction.     

Thermal ecology of two sympatric skinks (Mabuya macrorhyncha and Mabuya agilis] in a Brazilian restinga habitat

Abstract In a restinga habitat of southeastern Brazil, we studied some aspects of the thermal biology of two sympatric skinks (Mabuya macrorhyncha and Mabuya agilis) with distinct microhabitat preferences. The two species did not differ significantly in their mean body temperature. Sex and body size did not explain body temperature variation within either species. The body temperature of both species is significantly affected by air temperature, but only that of M. agilis is significantly influenced by sand surface temperature, presumably due to its more terrestrial habit compared to M. macrorhyncha. We found no significant seasonal variation in body temperature for either species, although environmental temperatures varied seasonally, indicating that both species may be selecting an optimal range of body temperatures, possibly through behavioural thermoregulation.     

El Niño Southern Oscillation and climate trends impact reservoir water quality

Low dissolved oxygen concentration in bottom layers of lakes and reservoirs usually indicates low water quality. In lakes, empirical models predicting anoxia are almost entirely based on the decay of plankton biomass, while in reservoirs recent findings suggest a prominent role of streamflow and load of organic carbon. This suggests a potential link between water quality in reservoirs and climate processes affecting streamflow. Here we support this hypothesis presenting evidence that both interannual climate variability and recent climate change, mainly consisting in a significant increase in potential evapotranspiration in the upstream basin, affected the oxygen content in a Mediterranean reservoir (Sau Reservoir, Spain). Using a 44‐year monthly record, we found strong and consistent signatures of El Niño Southern Oscillation in the inflow and reservoir oxygen content. Spectral and wavelet techniques showed that the El Niño, streamflow, and reservoir oxygen content series oscillated in common periods, which coincided with the main El Niño variability modes. An empirical model explaining the annual oxygen content in the reservoir suggested that a decreasing streamflow trend reduced the oxygen content of the reservoir by about 20%, counteracting remediation measures implemented at the basin upstream the reservoir. Our results provide the first quantitative evidence of climate change effects on reservoir water quality using long‐term instrumental data, and indicate that streamflow should be considered as a key variable in assessing climate change impact on reservoir water quality. These results are especially relevant in regions of the world where reservoirs are abundant and most climate models predict a decrease in runoff during the next decades. Both the expected trends and the sensitivity of reservoir water quality to global interannual climate variability should be considered for a correct management of water resources in the present and to design adaptation policies in the future.     

Footprints of climate change in the Arctic marine ecosystem

In this article, we review evidence of how climate change has already resulted in clearly discernable changes in marine Arctic ecosystems. After defining the term ‘footprint’ and evaluating the availability of reliable baseline information we review the published literature to synthesize the footprints of climate change impacts in marine Arctic ecosystems reported as of mid‐2009. We found a total of 51 reports of documented changes in Arctic marine biota in response to climate change. Among the responses evaluated were range shifts and changes in abundance, growth/condition, behaviour/phenology and community/regime shifts. Most reports concerned marine mammals, particularly polar bears, and fish. The number of well‐documented changes in planktonic and benthic systems was surprisingly low. Evident losses of endemic species in the Arctic Ocean, and in ice algae production and associated community remained difficult to evaluate due to the lack of quantitative reports of its abundance and distribution. Very few footprints of climate change were reported in the literature from regions such as the wide Siberian shelf and the central Arctic Ocean due to the limited research effort made in these ecosystems. Despite the alarming nature of warming and its strong potential effects in the Arctic Ocean the research effort evaluating the impacts of climate change in this region is rather limited.     

Temperature effects on oxygen thresholds for hypoxia in marine benthic organisms

The effect of warming on the oxygen requirements and the survival of benthic organisms under hypoxia was tested using a meta‐analysis of published results of experiments evaluating the effects of temperature on the median lethal time and median lethal concentration of benthic macrofauna under hypoxia. The meta‐analysis confirmed that survival times under hypoxia were reduced by on average 74% and that median lethal concentration increased by on average 16% when marine benthic organisms were exposed to warmer temperatures. Warming reduced survival times of marine benthic macrofauna under hypoxia by a median of 3.95±1.67 h °C^?1 and increased the oxygen thresholds for hypoxia‐driven mortality by a median of 1.02±0.15% saturation °C^?1 or 0.07±0.01 mg O₂ L^?1 °C^?1. The corresponding Q₁₀ values averaged 3.01±0.29 for the median survival time and 2.09±0.20 for the median lethal oxygen concentration. Use of these Q₁₀ values predicts that the 4 °C warming expected during the 21st century will lead to survival times 35.6% lower under hypoxia and that the threshold oxygen concentrations for high mortality to occur will increase by, on average, 25.5% if bottom water temperature increased by 4 °C. Hence, ocean warming is expected to increase the vulnerability of benthic macrofauna to reduced oxygen concentrations and expand the area of coastal ecosystems affected by hypoxia.     

Another new species of Ceratozamia (Zamiaceae) from Chiapas, Mexico

Ceratozamia mirandai sp. nov. from the Sepultura Biosphere reserve of Chiapas, Mexico, is described and illustrated. Its closest affinities are with C. kuesteriana Regel from Tamaulipas of north-east Mexico, but differs in male and female cone and trunk morphology.     

Evolution in caves: Darwin’s ‘wrecks of ancient life’ in the molecular era

Cave animals have historically attracted the attention of evolutionary biologists because of their bizarre ‘regressive’ characters and convergent evolution. However, understanding of their biogeographic and evolutionary history, including mechanisms of speciation, has remained elusive. In the last decade, molecular data have been obtained for subterranean taxa and their surface relatives, which have allowed some of the classical debates on the evolution of cave fauna to be revisited. Here, we review some of the major studies, focusing on the contribution of phylogeography in the following areas: biogeographic history and the relative roles of dispersal and vicariance, colonization history, cryptic species diversity and modes of speciation of cave animals. We further consider the limitations of current research and prospects for the future. Phylogeographic studies have confirmed that cave species are often cryptic, with highly restricted distributions, but have also shown that their divergence and potential speciation may occur despite the presence of gene flow from surface populations. Significantly, phylogeographic studies have provided evidence for speciation and adaptive evolution within the confines of cave environments, questioning the assumption that cave species evolved directly from surface ancestors. Recent technical developments involving ‘next generation’ DNA sequencing and theoretical developments in coalescent and population modelling are likely to revolutionize the field further, particularly in the study of speciation and the genetic basis of adaptation and convergent evolution within subterranean habitats. In summary, phylogeographic studies have provided an unprecedented insight into the evolution of these unique fauna, and the future of the field should be inspiring and data rich.     

Spermiogenesis and sperm morphology in the marine gastropod Nucella crassilabrum with an account of morphometric patterns of spermatozoa variation in the family Muricidae

Abstract

Spermatid differentiation and the morphology of mature spermatozoa in Nucella crassilabrum, a muricid snail, was investigated. Five phases of spermiogenesis considering the polarization of organelles, nuclear elongation and chromatin condensation are described. Characteristics observed are compared to those of other muricaceans gastropods. The comparison of the proportional size of the different sperm segments (head, middle- and principal piece) between these species, is emphasized.

Two morphometric patterns of sperm structure are distinguished and their functional significance discussed. The relative size attained by the different sperm segments within each of these patterns, could be the result of the combined effect of at least two types of factors: first, those determining the proportional size (length) of the head and, secondly, those factors conditioning the energy requirements of the gamete thus influencing the relative development of the middle- and principal piece.     

The radiation of Satyrini butterflies (Nymphalidae: Satyrinae): a challenge for phylogenetic methods

We have inferred the most comprehensive phylogenetic hypothesis to date of butterflies in the tribe Satyrini. In order to obtain a hypothesis of relationships, we used maximum parsimony and model‐based methods with 4435 bp of DNA sequences from mitochondrial and nuclear genes for 179 taxa (130 genera and eight out‐groups). We estimated dates of origin and diversification for major clades, and performed a biogeographic analysis using a dispersal–vicariance framework, in order to infer a scenario of the biogeographical history of the group. We found long‐branch taxa that affected the accuracy of all three methods. Moreover, different methods produced incongruent phylogenies. We found that Satyrini appeared around 42 Mya in either the Neotropical or the Eastern Palaearctic, Oriental, and/or Indo‐Australian regions, and underwent a quick radiation between 32 and 24 Mya, during which time most of its component subtribes originated. Several factors might have been important for the diversification of Satyrini: the ability to feed on grasses; early habitat shift into open, non‐forest habitats; and geographic bridges, which permitted dispersal over marine barriers, enabling the geographic expansions of ancestors to new environments that provided opportunities for geographic differentiation, and diversification.

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