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Biology Letters

Barry W Brook, John Alroy
Extinction is a key feature of the evolutionary history of life, and assessments of extinction risk are essential for the effective protection of biodiversity. The goal in assembling this special issue of Biology Letters was to highlight problems and questions at the research frontier of extinction biology, with an emphasis on recent developments in the methodology of inferring the patterns and processes of extinction from a background of often noisy and sparse data. In selecting topics, we sought to illustrate how extinction is not simply a self-evident phenomenon, but the subject of a dynamic and quantitatively rigorous field of natural science, with practical applications to conservation...
January 2017: Biology Letters
Isabelle Maréchaux, Megan K Bartlett, Amaia Iribar, Lawren Sack, Jérôme Chave
Pan-tropically, liana density increases with decreasing rainfall and increasing seasonality. This pattern has led to the hypothesis that lianas display a growth advantage over trees under dry conditions. However, the physiological mechanisms underpinning this hypothesis remain elusive. A key trait influencing leaf and plant drought tolerance is the leaf water potential at turgor loss point (πtlp). πtlp adjusts under drier conditions and this contributes to improved leaf drought tolerance. For co-occurring Amazonian tree (n = 247) and liana (n = 57) individuals measured during the dry and the wet seasons, lianas showed a stronger osmotic adjustment than trees...
January 2017: Biology Letters
Gabrielle L Davidson, Alex Thornton, Nicola S Clayton
Strong selection pressures are known to act on animal coloration. Although many animals vary in eye colour, virtually no research has investigated the functional significance of these colour traits. Passeriformes have a range of iris colours, making them an ideal system to investigate how and why iris colour has evolved. Using phylogenetic comparative methods, we tested the hypothesis that conspicuous iris colour in passerine birds evolved in response to (a) coordination of offspring care and (b) cavity nesting, two traits thought to be involved in intra-specific gaze sensitivity...
January 2017: Biology Letters
Jenélle Dowling, Michael S Webster
When mates are limited, individuals should allocate resources to mating tactics that maximize fitness. In species with extra-pair paternity (EPP), males can invest in mate guarding, or, alternatively, in seeking EPP. Males should optimize fitness by adjusting investment according to their attractiveness to females, such that attractive males seek EPP, and unattractive males guard mates. This theory has received little empirical testing, leaving our understanding of the evolution of mating tactics incomplete; it is unclear how a male's relative attractiveness influences his tactics...
January 2017: Biology Letters
Xiaowei Cui, Weimin Song, Jianxiang Feng, Dai Jia, Jiemin Guo, Zhonglei Wang, Hao Wu, Fei Qi, Jie Liang, Guanghui Lin
Mangroves in China are severely affected by the rapid invasion of the non-native species Spartina alterniflora Although many studies have addressed the possible impacts of S. alterniflora on the performance of mangrove seedlings, how excessive nitrogen (N) input due to eutrophication affects the interactions between mangrove species and S. alterniflora remains unknown. Here, we report the results from a mesocosm experiment using seedlings of the native mangrove species Kandelia obovata and the exotic S. alterniflora grown in monoculture and mixed culture under no nitrogen addition and nitrogen (N) addition treatments for 18 months...
January 2017: Biology Letters
Suzanne McGaugh, Tonia S Schwartz
Endothermy is an evolutionary innovation in eutherian mammals and birds. In eutherian mammals, UCP1 is a key protein in adaptive nonshivering thermogenesis (NST). Although ucp1 arose early in the vertebrate lineage, the loss of ucp1 was previously documented in several reptile species (including birds). Here we determine that ucp1 was lost at the base of the reptile lineage, as we fail to find ucp1 in every major reptile lineage. Furthermore, though UCP1 plays a key role in mammalian NST, we confirm that pig has lost several exons from ucp1 and conclude that pig is not a sole outlier as the only eutherian mammal lineage to do so...
January 2017: Biology Letters
Laura Gangoso, Rafael Gutiérrez-López, Josué Martínez-de la Puente, Jordi Figuerola
Individual genetic diversity is predicted to influence host-parasite interactions. Together with the genes directly associated with immune responses, variation in genes regulating vertebrate melanin-based pigmentation may play an important role in these interactions, mainly through the pleiotropic effects that affect colour-specific physiology, behaviour and immunity. Here, we test the hypothesis that the prevalence of avian malarial parasites differs between phenotypes in a raptor species in which the genetic basis of colour polymorphism and its pleiotropic effects over immune functions are known...
December 2016: Biology Letters
Stav Talal, Amir Ayali, Eran Gefen
The adaptive nature of discontinuous gas exchange (DGE) in insects is contentious. The classic 'hygric hypothesis', which posits that DGE serves to reduce respiratory water loss (RWL), is still the best supported. We thus focused on the hygric hypothesis in this first-ever experimental evolution study of any of the competing adaptive hypotheses. We compared populations of the migratory locust (Locusta migratoria) that underwent 10 consecutive generations of selection for desiccation resistance with control populations...
December 2016: Biology Letters
Henrik Skov, Mark Desholm, Stefan Heinänen, Johnny A Kahlert, Bjarke Laubek, Niels Einar Jensen, Ramūnas Žydelis, Bo Præstegaard Jensen
Monitoring of bird migration at marine wind farms has a short history, and unsurprisingly most studies have focused on the potential for collisions. Risk for population impacts may exist to soaring migrants such as raptors with K-strategic life-history characteristics. Soaring migrants display strong dependence on thermals and updrafts and an affinity to land areas and islands during their migration, a behaviour that creates corridors where raptors move across narrow straits and sounds and are attracted to islands...
December 2016: Biology Letters
Graziella Iossa, Matthew J G Gage, Paul E Eady
In the majority of insects, sperm fertilize the egg via a narrow canal through the outer chorion called the micropyle. Despite having this one primary function, there is considerable unexplained variation in the location, arrangement and number of micropyles within and between species. Here, we examined the relationship between micropyle number and female mating pattern through a comparative analysis across Lepidoptera. Three functional hypotheses could explain profound micropylar variation: (i) increasing micropyle number reduces the risk of infertility through sperm limitation in species that mate infrequently; (ii) decreasing micropyle number reduces the risk of pathological polyspermy in species that mate more frequently; and (iii) increasing micropyle number allows females to exert greater control over fertilization within the context of post-copulatory sexual selection, which will be more intense in promiscuous species...
December 2016: Biology Letters
Lisandrina Mari, Laura Garaud, Guillaume Evanno, Emilien Lasne
In a warming climate, higher temperatures are likely to modulate positively or negatively the effect of other environmental factors on biota, although such interactions are poorly documented. Here, we explore under controlled conditions the combined effects of two common stressors in freshwater ecosystems, higher temperature and sediment load, on the embryonic development of arctic charr (Salvelinus alpinus L.). In the warm treatment, embryos had a lower survival, a longer incubation period and a smaller body size with a bigger yolk sac volume...
December 2016: Biology Letters
Christina Ebneter, Joel L Pick, Barbara Tschirren
Natural selection favours increased investment in reproduction, yet considerable variation in parental investment is observed in natural populations. Life-history theory predicts that this variation is maintained by a trade-off between the benefits of increased reproductive investment and its associated costs for the parents. The nature of these costs of reproduction, however, remains poorly understood. The brain is an energetically highly expensive organ and increased reproductive investment may, therefore, negatively affect brain maintenance...
December 2016: Biology Letters
Mirjam Appel, Claus-Jürgen Scholz, Samet Kocabey, Sinead Savage, Christian König, Ayse Yarali
A painful event establishes two opponent memories: cues that are associated with pain onset are remembered negatively, whereas cues that coincide with the relief at pain offset acquire positive valence. Such punishment- versus relief-memories are conserved across species, including humans, and the balance between them is critical for adaptive behaviour with respect to pain and trauma. In the fruit fly, Drosophila melanogaster as a study case, we found that both punishment- and relief-memories display natural variation across wild-derived inbred strains, but they do not covary, suggesting a considerable level of dissociation in their genetic effectors...
December 2016: Biology Letters
Ethan G Staats, Salvatore J Agosta, James R Vonesh
Changes in predator diversity via extinction and invasion are increasingly widespread and can have important ecological and socio-economic consequences. Anticipating and managing these consequences requires understanding how predators shape ecological communities. Previous predator biodiversity research has focused on post-colonization processes. However, predators can also shape communities by altering patterns of prey habitat selection during colonization. The sensitivity of this non-consumptive top down mechanism to changes in predator diversity is largely unexamined...
December 2016: Biology Letters
David W Armitage
No abstract text is available yet for this article.
December 2016: Biology Letters
Markus Zöttl, Jack Thorley, David Gaynor, Nigel C Bennett, Tim Clutton-Brock
In some eusocial insect societies, adaptation to the division of labour results in multimodal size variation among workers. It has been suggested that variation in size and growth among non-breeders in naked and Damaraland mole-rats may similarly reflect functional divergence associated with different cooperative tasks. However, it is unclear whether individual growth rates are multimodally distributed (as would be expected if variation in growth is associated with specialization for different tasks) or whether variation in growth is unimodally distributed, and is related to differences in the social and physical environment (as would be predicted if there are individual differences in growth but no discrete differences in developmental pathways)...
December 2016: Biology Letters
Eric Post, Jeffrey Kerby, Christian Pedersen, Heidi Steltzer
We analysed 12 years of species-specific emergence dates of plants at a Low-Arctic site near Kangerlussuaq, Greenland to investigate associations with sea ice dynamics, a potential contributor to local temperature variation in near-coastal tundra. Species displayed highly variable rates of phenological advance, from a maximum of -2.55 ± 0.17 and -2.93 ± 0.51 d yr(-1) among a graminoid and forb, respectively, to a minimum of -0.55 ± 0.19 d yr(-1) or no advance at all in the two deciduous shrub species. Monthly Arctic-wide sea ice extent was a significant predictor of emergence timing in 10 of 14 species...
December 2016: Biology Letters
P Morán, L Labbé, C Garcia de Leaniz
Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development...
December 2016: Biology Letters
Eric V Regehr, Kristin L Laidre, H Resit Akçakaya, Steven C Amstrup, Todd C Atwood, Nicholas J Lunn, Martyn Obbard, Harry Stern, Gregory W Thiemann, Øystein Wiig
Loss of Arctic sea ice owing to climate change is the primary threat to polar bears throughout their range. We evaluated the potential response of polar bears to sea-ice declines by (i) calculating generation length (GL) for the species, which determines the timeframe for conservation assessments; (ii) developing a standardized sea-ice metric representing important habitat; and (iii) using statistical models and computer simulation to project changes in the global population under three approaches relating polar bear abundance to sea ice...
December 2016: Biology Letters
Scott Davies, Kendra B Sewall
No abstract text is available yet for this article.
November 2016: Biology Letters
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