Island and mainland populations of animal species often differ strikingly in lifehistory traits such as clutch size, egg size, total reproductive effort and body size. However, despite widespread recognition of insular shifts in these life-history traits in birds, mammals and reptiles, there have been no reports of such life-history shifts in amphibians. Furthermore, most studies have focused on one specific lifehistory trait without explicit consideration of coordinated evolution among these intimately linked life-history traits, and thus the relationships among these traits are poorly studied. Here we provide the first evidence of insular shifts and tradeoffs in a coordinated suite of life-history traits for an amphibian species, the pond frog Rana nigromaculata. Life-history data were collected from eight islands in the Zhoushan Archipelago and neighboring mainland China. We found consistent, significant shifts in all life-history traits between mainland and island populations. Island populations had smaller clutch sizes, larger egg sizes, larger female body size and invested less in total reproductive effort than mainland populations. Significant negative relationships were found between egg size and clutch size and between egg size and total reproductive effort among frog populations after controlling for the effects of body size. Therefore, decreased reproductive effort and clutch size, larger egg size and body size in pond frogs on islands were selected through trade-offs as an overall life-history strategy. Our findings contribute to the formation of a broad, repeatable ecological generality for insular shifts in lifehistory traits across a range of terrestrial vertebrate taxa.
The Chinese alligator Alligator sinensis is a critically endangered species endemic to China, and one of the most endangered crocodilian species in the world. Like many other reptiles, important aspects of alligator biology such as foraging, timing of hibernation, breeding and the sex ratio of offspring are all affected by temperature variation. We examined the effects of long-term temperature change on oviposition dates and clutch sizes of the Chinese alligator in a semi-natural facility in southern China. Our study focused on two captive generations including an old breeding generation captured from the wild and a generation composed of their F1 offspring. Median oviposition date shifted to earlier in the year and mean clutch size was larger for both generations as the monthly mean air temperature in April increased over the 19 years of data collection. We observed a mean advance in oviposition date of 10 days for the old breeding generation from 1987 to 2005 and 8 days for both generations from 1991 to 2005. Correspondingly, clutch sizes for the two generations also increased during this period. There were no differences in median oviposition dates and clutch sizes between the two generations from 1991 to 2005. Our results suggest that Chinese alligators have responded to increasing global temperatures. Our findings also suggest that recent increasing global temperatures have the potential to have a substantial effect on Chinese alligator populations in the wild, thus prompting an urgent need for field monitoring of the effects of global warming on this endangered alligator species.
The Helan Shan pika Ochotona argentata is an Endangered pika endemic to Ningxia Helan Shan National Nature Reserve in China. Little is known about the species, including regarding its population status, distribution, habitat requirements and even basic natural history. We conducted camera trapping in the Reserve during 13 January 2020–25 January 2022 and obtained two new records for this species. These, combined with five other new records obtained during the monitoring programme in the Reserve, represent a significant increase in the known range of the species and more than double the species’ known extent of occurrence from 107 to 223 km2. These records also provide the first evidence that this species is active both nocturnally and diurnally. However, this range increase does not alter the Endangered status of the pika, and the pika was not observed within its previously known range; future research should involve intensive camera trapping in the Reserve to ascertain whether this is a result of local extirpation, habitat loss or fragmentation or under-sampling on our part. Studies should also incorporate techniques used for other alpine pika species to collect baseline data on habitat use, population size and behaviour to determine the potential response of the Helan Shan pika to present and future threats.
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