Martha L. Calderón-Espinosa

Bio: Martha L. Calderón-Espinosa is an academic researcher from National University of Colombia. The author has contributed to research in topics: Anolis & Dactyloidae. The author has an hindex of 8, co-authored 21 publications receiving 1442 citations. Previous affiliations of Martha L. Calderón-Espinosa include National Autonomous University of Mexico.

Erosion of lizard diversity by climate change and altered thermal niches.

Abstract: It is predicted that climate change will cause species extinctions and distributional shifts in coming decades, but data to validate these predictions are relatively scarce Here, we compare recent and historical surveys for 48 Mexican lizard species at 200 sites Since 1975, 12% of local populations have gone extinct We verified physiological models of extinction risk with observed local extinctions and extended projections worldwide Since 1975, we estimate that 4% of local populations have gone extinct worldwide, but by 2080 local extinctions are projected to reach 39% worldwide, and species extinctions may reach 20% Global extinction projections were validated with local extinctions observed from 1975 to 2009 for regional biotas on four other continents, suggesting that lizards have already crossed a threshold for extinctions caused by climate change

Evolution of egg retention in the sceloporus spinosus group: exploring the role of physiological, environmental, and phylogenetic factors

Abstract: The evolution of viviparity in squamates has involved intermediate stages of egg retention. Reduction in the thickness of the eggshell, in relative clutch mass (RCM), and in clutch frequency would have facilitated the transition from oviparity to viviparity, while low temperatures are likely the ultimate selective force that promoted this evolutionary shift. We tested these ideas using the Sceloporus spinosus group. Because it is the sister clade of the viviparous Sceloporus formosus group, we predicted that mem- bers of the S. spinosus group would exhibit extended egg retention and other features associated with the evolution of viviparity. To test this idea, we examined the ability to retain eggs past the time of normal oviposition in the Sceloporus spinosus group and evaluated the association between egg retention and physiological and environmental factors in a historical context. Gravid females were collected from seven localities at a wide range of altitudes. We estimated the normal stage of embryos at oviposition and the stage at oviposition when females were induced to retain eggs under captive conditions. Stages of embryos varied within clutches; less developed embryos were usually dead and the most advanced embryos were usually alive. The maximum stage observed was therefore used as an index of egg retention for each clutch. The maximum embryonic stage at oviposition was contrasted with RCM, egg membrane thick- ness, and several climatic variables (temperature and precipitation) in a phylogenetic framework. Females exhibited the ability to retain eggs as predicted. Maximum stage at oviposition varied within same clutch, same locality, and among localities. Variation observed in the maximum stage at oviposition was not related to egg membrane thickness, RCM, or clutch frequency or to environmental temperature and precipita- tion. Instead, mapping the maximum stage at oviposition on a phylogeny of the S. spinosus group suggested that the invasion of high elevations was associated with an enhanced potential for longer periods of egg retention.

Reproductive Activity of Three Sympatric Viviparous Lizards at Omiltemi, Guerrero, Sierra Madre del Sur, Mexico

Abstract: We studied the reproductive characteristics of sympatric populations of Sceloporus formosus scitulus, Sceloporus omiltemanus (Phrynosomatidae), and Mesaspis gadovii (Anguidae) at the Omiltemi forest reserve (Guerrero, Mexico). Males are larger and reach larger body sizes at reproductive maturity and are more colorful than females in both Sceloporus, whereas males are smaller than females and reach sexual maturity at similar body sizes in M. gadovii. These species are single brooded and follow a common pattern of annual reproductive activity. The reproductive activity of females and males of the three species is seasonal; vitellogenesis is initiated in late summer and continues in autumn/rainy season, gestation occurs throughout the winter/dry season, and parturition occurs in early spring. All three species have intersexual synchrony in reproductive activity. In spite of similar reproductive schedules, some subtle features related to the length of each of the reproductive stages could be observed. Sceloporus formosus scitulus has a more extended reproductive season, and large females start vitellogenesis earlier than do small ones. Males have a prolonged reproductive activity and a short nonreproductive season. In contrast, the reproductive cycle of the other two species is defined by shorter reproductive season and less intrasexual asynchrony for both sexes than found in S. f. scitulus. The seasonal pattern of reproduction shared by these three species is characteristic of other viviparous lizards at high elevations in tropical and subtropical latitudes of Central and South America, being convergent for different lizard families. This convergence in reproductive patterns suggests a common evolutionary response to environmental factors associated with montane habitats, whereas specific differences observed within species are attributed to the particular evolutionary history of each taxon.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Rapid Range Shifts of Species Associated with High Levels of Climate Warming

Abstract: The distributions of many terrestrial organisms are currently shifting in latitude or elevation in response to changing climate Using a meta-analysis, we estimated that the distributions of species have recently shifted to higher elevations at a median rate of 110 meters per decade, and to higher latitudes at a median rate of 169 kilometers per decade These rates are approximately two and three times faster than previously reported The distances moved by species are greatest in studies showing the highest levels of warming, with average latitudinal shifts being generally sufficient to track temperature changes However, individual species vary greatly in their rates of change, suggesting that the range shift of each species depends on multiple internal species traits and external drivers of change Rapid average shifts derive from a wide diversity of responses by individual species

Has the Earth’s sixth mass extinction already arrived?

Abstract: Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis. Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.