Optimal reproductive phenology under size‐dependent cannibalism

Intra‐cohort cannibalism is an example of a size‐mediated priority effect. If early life stages cannibalize slightly smaller individuals, then parents face a trade‐off between breeding at the best time for larval growth or development and predation risk from offspring born earlier. This game‐theoretic situation among parents may drive adaptive reproductive phenology toward earlier breeding. However, it is not straightforward to quantify how cannibalism affects seasonal egg fitness or to distinguish emergent breeding phenology from alternative adaptive drivers. Here, we devise an age‐structured game‐theoretic mathematical model to find evolutionary stable breeding phenologies. We predict how size‐dependent cannibalism acting on eggs, larvae, or both changes emergent breeding phenology and find that breeding under inter‐cohort cannibalism occurs earlier than the optimal match to environmental conditions. We show that emergent breeding phenology patterns at the level of the population are sensitive to the ontogeny of cannibalism, that is, which life stage is subject to cannibalism. This suggests that the nature of cannibalism among early life stages is a potential driver of the diversity of reproductive phenologies seen across taxa and may be a contributing factor in situations where breeding occurs earlier than expected from environmental conditions.     

Fine-Scale Genetic Structure and Demographic History in the Miyako Islands of the Ryukyu Archipelago

The Ryukyu Archipelago is located in the southwest of the Japanese islands and is composed of dozens of islands, grouped into the Miyako Islands, Yaeyama Islands, and Okinawa Islands. Based on the results of principal component analysis on genome-wide single-nucleotide polymorphisms, genetic differentiation was observed among the island groups of the Ryukyu Archipelago. However, a detailed population structure analysis of the Ryukyu Archipelago has not yet been completed. We obtained genomic DNA samples from 1,240 individuals living in the Miyako Islands, and we genotyped 665,326 single-nucleotide polymorphisms to infer population history within the Miyako Islands, including Miyakojima, Irabu, and Ikema islands. The haplotype-based analysis showed that populations in the Miyako Islands were divided into three subpopulations located on Miyakojima northeast, Miyakojima southwest, and Irabu/Ikema. The results of haplotype sharing and the D statistics analyses showed that the Irabu/Ikema subpopulation received gene flows different from those of the Miyakojima subpopulations, which may be related with the historically attested immigration during the Gusuku period (900 − 500 BP). A coalescent-based demographic inference suggests that the Irabu/Ikema population firstly split away from the ancestral Ryukyu population about 41 generations ago, followed by a split of the Miyako southwest population from the ancestral Ryukyu population (about 16 generations ago), and the differentiation of the ancestral Ryukyu population into two populations (Miyako northeast and Okinawajima populations) about seven generations ago. Such genetic information is useful for explaining the population history of modern Miyako people and must be taken into account when performing disease association studies.     

The Rate of Cu,Zn Superoxide Dismutase Evolution

The rate of amino acid replacement in Cu, Zn SOD greatly departs from the expectations of the molecular clock. We examine 27 Cu, Zn SOD sequences available and conclude that: (I) the SOD enzymes from different mammal families differ from each other by roughly the same number of replacements, which is consistent with a simultaneous mammalian radiation; (2) over the most recent 60 million years (MY) the rate of SOD evolution is fairly high (15aa/100aa/100MYR) and may be considered constant; (3) the rate of accumulation of amino acid replacements since the divergence of fungi. plants and animals to the present is inconstant along different branches of the evolutionary tree; moreover it steadily decreases with time, to the same extent in all lineages; (4) some comparisons exhibit divergences that are in any case greater than expected from a Poisson process on the assumption of a molecular clock; (5) plant chloroplast enzymes display fewer differences from each other than cytoplasmic ones; (6) bacteriocuprein (from Photobacterium leiognathi), fluke and human extracellular SOD are all three extremely remotely related to one another and to the SOD of other eukaryotes.

The process of consistent decline of the rate of evolution of Cu. Zn SOD can be described by a number of mathematical functions. We explore simple models that assume constant rates and might be applicable to other proteins or genes that apparently evolve at disparate rates.     

Flight loss linked to faster molecular evolution in insects

The loss of flight ability has occurred thousands of times independently during insect evolution. Flight loss may be linked to higher molecular evolutionary rates because of reductions in effective population sizes (N_e) and relaxed selective constraints. Reduced dispersal ability increases population subdivision, may decrease geographical range size and increases (sub)population extinction risk, thus leading to an expected reduction in N_e. Additionally, flight loss in birds has been linked to higher molecular rates of energy-related genes, probably owing to relaxed selective constraints on energy metabolism. We tested for an association between insect flight loss and molecular rates through comparative analysis in 49 phylogenetically independent transitions spanning multiple taxa, including moths, flies, beetles, mayflies, stick insects, stoneflies, scorpionflies and caddisflies, using available nuclear and mitochondrial protein-coding DNA sequences. We estimated the rate of molecular evolution of flightless (FL) and related flight-capable lineages by ratios of non-synonymous-to-synonymous substitutions (dN/dS) and overall substitution rates (OSRs). Across multiple instances of flight loss, we show a significant pattern of higher dN/dS ratios and OSRs in FL lineages in mitochondrial but not nuclear genes. These patterns may be explained by relaxed selective constraints in FL ectotherms relating to energy metabolism, possibly in combination with reduced N_e.     

Past and present distributions of southern right whales(Eubalaena australis)

Abstract

During the 19th century, sail whalers hunted right whales throughout the southern oceans north of 50 degrees. This review seeks to document the recovery of southern right whales by comparing the northernmost recent sightings with older sightings that survive “fossilised” in historical records of the sail whaling era. Despite a steady expansion northwards in recent years, the present distribution of right whales is still far short of that recorded by sail whalers over a century ago.     

Demography of greenbug,Schizaphis graminum (Rondani) (Hemiptera: Aphididae) on six barley cultivars

The greenbugs, Schizaphis graminum (Rondani) were collected from the barley fields in Isfahan region of Iran. The aphid colonies were maintained on each of six barley cultivars including Karoon, Kavir, Zarjoo, Nosrat, Afzal and Rihane. All the experiments were done on the mentioned barley varieties at 26 ± 1°C, 60 ± 5% relative humidity (RH) and at a photoperiod of 16:8 (L:D) h. The shortest and longest developmental times were obtained on Nosrat 6.35 ± 0.11 and Rihane 6.75 ± 0.07 days, respectively. The survivorship of immature stages varied from 71.95% on Nosrat to 82.14% on Zarjoo. The total number of offsprings were 71.05 and 63.22 nymphs per female on Kavir and Karoon. The highest and lowest r _m values were observed on Kavir (0.336 ± 0.005) and Rihane (0.299 ± 0.008), respectively. The statistical analysis of jackknife did not show a significant influence of the tested barley varieties for the mean generation time and a similar procedure of difference for λ and r _m was estimated.     

Intrinsic vs. extrinsic influences on life history expression: metabolism and parentally induced temperature influences on embryo development rate

Intrinsic processes are assumed to underlie life history expression and trade‐offs, but extrinsic inputs are theorised to shift trait expression and mask trade‐offs within species. Here, we explore application of this theory across species. We do this based on parentally induced embryo temperature as an extrinsic input, and mass‐specific embryo metabolism as an intrinsic process, underlying embryonic development rate. We found that embryonic metabolism followed intrinsic allometry rules among 49 songbird species from temperate and tropical sites. Extrinsic inputs via parentally induced temperatures explained the majority of variation in development rates and masked a relationship with metabolism; metabolism explained a minor proportion of the variation in development rates among species, and only after accounting for temperature effects. We discuss evidence that temperature further obscures the expected interspecific trade‐off between development rate and offspring quality. These results demonstrate the importance of considering extrinsic inputs to trait expression and trade‐offs across species.     

Ecological interactions in Aedes species on Reunion Island

Two invasive, container‐breeding mosquito species, Aedes aegypti (Stegomyia aegypti) and Aedes albopictus (Stegomyia albopicta) (Diptera: Culicidae), have different distribution patterns on Reunion Island. Aedes albopictus occurs in all areas and Ae. aegypti colonizes only some restricted areas already occupied by Ae. albopictus. This study investigates the abiotic and biotic ecological mechanisms that determine the distribution of Aedes species on Reunion Island. Life history traits (duration of immature stages, survivorship, fecundity, estimated finite rate of increase) in Ae. aegypti and Ae. albopictus were compared at different temperatures. These fitness measures were characterized in both species in response to competitive interactions among larvae. Aedes aegypti was drastically affected by temperature, performing well only at around 25 °C, at which it achieved its highest survivorship and greatest estimated rate of increase. The narrow distribution of this species in the field on Reunion Island may thus relate to its poor ability to cope with unfavourable temperatures. Aedes aegypti was also more negatively affected by high population densities and to some extent by interactions with Ae. albopictus, particularly in the context of limited food supplies. Aedes albopictus exhibited better population performance across a range of environmental conditions. Its ecological plasticity and its superior competitive ability relative to its congener may further enhance its invasion success on Reunion Island.     

Conservation implications of adaptation to tropical climates from a historical perspective

Tropical climates and the biodiversity associated with them have long interested natural historians. Alexander von Humboldt inspired a generation of scientists, such as Charles Darwin and Alfred Russel Wallace, to observe and study tropical ecosystems. More recently, the mid‐20th century saw Theodosius Dobzhansky and Daniel Janzen lay the foundations for studying adaptation to tropical climates. Now in the 21st century, we are beginning to realize the threats posed by current and future climate change to tropical populations which, despite relatively low levels of projected warming for low‐latitude regions, face potentially significant detrimental impacts. Building on the insights of researchers in decades and centuries past, improved understanding of tropical ecology, evolution and biogeography will help us to conceive how future global change will impact on biodiversity.     

Temperature and embryonic development in polar marine invertebrates

The life-history tactics of many Antarctic marine invertebrates suggest that the commonly observed slow rates of growth are adaptations to the pattern of food availability, and not due to low temperature per se. This implies that marine invertebrates have been able, over the course of evolutionary time, to compensate their rates of embryonic development for the effect of temperature. Data from north Atlantic copepods indicate that this is so. It is therefore suggested that the slow rates of embryonic development in many Antarctic marine invertebrates are the result of large egg size, and not the low temperature. Large, slowly developing eggs are part of a suite of tactics, often called K-strategies, which characterise many marine invertebrates in Antarctica.