Interactive effect matters: a combination of herbivory degree and the ratio of generalist to specialist better predicts evolution of plant defense

Herbivory degree and the ratio of generalist to specialist herbivores have long been treated as two important but independent factors in shaping the evolution of plant defense. However, this assumption of independency is poorly supported and has resulted in great controversy in explaining the patterns of plant defense. Here we investigated the possible interaction between herbivory degree and generalist-to-specialist ratio using a cost-benefit model of defense evolution in plants. Our results showed that, with increasing generalist herbivore proportion, plant defense investment increases when herbivory degree is low and decreases when herbivory degree is high. These results provide the first theoretical support for the interactive effect of herbivory degree and ratio of generalist/specialist affecting plant defense, which integrate many of the previous results (e.g. latitudinal patterns of plant defense and defense evolution of invasive plants) and put them into a more general theoretical context.

Local climate and vernalization requirements explain the latitudinal patterns of flowering initiation in the crop wild relative Linum bienne

Background and Aims: Days to flowering initiation in species with large geographic distributions often correlate with latitude. Latitude reflects climatic gradients, but it is unclear if large-scale differentiation in flowering results from adaptation to local climate, and whether adaptation to local climate could constrain shifts in distribution and colonization of new environments. Methods: In its Western range in Europe, L. bienne populations were surveyed to describe latitudinal patterns of flowering initiation and determine its correlation with the local climate of populations. This was measured under standardized greenhouse conditions, with a vernalization experiment to learn if chilling advances flowering, and with a reciprocal transplant experiment at three sites along the latitudinal gradient, recording flowering at the central site and plant survival in all sites. Also, genetic differentiation of populations along the latitudinal range was studied using microsatellite markers. Key Results: Flowering initiation varied with latitude, with southern populations flowering earlier than northern populations. Latitude also predicted population response to vernalization, with chilling inducing a greater advance of flowering initiation in northern than southern populations. In general, plant survival in the reciprocal transplant experiment decreased with the geographic distance of populations to the experimental site and, at the central site, flowering initiation varied with latitude of origin. However, across experiments, the local climate of populations better predicted the differentiation in flowering initiation and vernalization response than latitude of origin. Finally, the microsatellite data revealed genetic differentiation of populations forming two groups that agree with a Mediterranean and Atlantic lineage. Conclusions: The consistent result across experiments of a latitudinal cline in flowering initiation and in the vernalization response suggests that flowering is under genetic regulation and yet dependent on particular environmental and climatic cues at local scale. However, the genetic differentiation suggests that past population history might influenced the flowering initiation patterns detected.

A comprehensive assessment of the intertidal biodiversity along the Portuguese coast in the early 2000s

The unprecedented rates of current biodiversity loss have motivated a renewed interest in environmental and biodiversity monitoring. The need for sustained monitoring strategies has prompted not only the establisment of new long-term monitoring programmes, but also the rescue of data from historical or otherwise archived sources. Amongst the most valuable datasets are those containing information on intertidal systems, as they are particularly well suited for studying the biological effects of climate change. The Portuguese rocky coast is quite interesting for studying the effects of climate change on the distribution of species due to its geographical orientation, latitudinal patterns in temperature, species richness, species' distribution patterns and availability of historical information. This work aims at providing a comprehensive picture of the distribution and abundance of intertidal macro-invertebrates and macro-algae along the Portuguese rocky coast in the early 2000s. This study provides a description of the rocky shore intertidal biodiversity of the mainland Portuguese coast in the early 2000s. The spatial distribution and semi-quantitative abundance of a total of 238 taxa were assessed at 49 wave-exposed locations. These data provide a comprehensive baseline against which biodiversity changes can be effectively and objectively evaluated.

Body and wing size, but not wing shape, vary along a large-scale latitudinal gradient in a damselfly

Large-scale latitudinal studies that include both north and south edge populations and address sex differences are needed to understand how selection has shaped trait variation. We quantified the variation of flight-related morphological traits (body size, wing size, ratio between wing size and body size, and wing shape) along the whole latitudinal distribution of the damselfly Lestes sponsa, spanning over 2700 km. We tested predictions of geographic variation in the flight-related traits as a signature of: (1) stronger natural selection to improve dispersal in males and females at edge populations; (2) stronger sexual selection to improve reproduction (fecundity in females and sexual behaviors in males) at edge populations. We found that body size and wing size showed a U-shaped latitudinal pattern, while wing ratio showed the inverse shape. However, wing shape varied very little along the latitudinal gradient. We also detected sex-differences in the latitudinal patterns of variation. We discuss how latitudinal differences in natural and sexual selection regimes can lead to the observed quadratic patterns of variation in body and wing morphology via direct or indirect selection. We also discuss the lack of latitudinal variation in wing shape, possibly due to aerodynamic constraints.

High biogeographic and latitudinal variability in gastropod drilling predation on molluscs along the eastern Indian coast: Implications on the history of fossil record of drillholes

Studies on the large-scale latitudinal patterns of gastropod drilling predation reveal that predation pressure may decrease or increase with increasing latitude, or even show no trend, questioning the generality of any large-scale latitudinal or biogeographic pattern. Here, we analyze the nature of spatio-environmental and latitudinal variation in gastropod drilling along the Indian eastern coast by using 76 samples collected from 39 locations, covering ~2500 km, incorporating several ecoregions, and ~15° latitudinal extents. We find no environmental or latitudinal gradient. In fact, drilling intensity varies highly within the same latitudinal bin, or oceanic sub-basins, or even the same ecoregions. Moreover, different ecoregions with their distinctive biotic and abiotic environmental variables show similar predation intensities. However, one pattern is prevalent: some small infaunal prey taxa, living in the sandy-muddy substrate—which are preferred by the naticid gastropods—are always attacked more frequently over others, indicating taxon and size selectivity by the predators. The result suggests that the biotic and abiotic factors, known to influence drilling predation, determine only the local predation pattern. In the present case, the nature of substrate and prey composition determines the local predation intensity: soft substrate habitats host dominantly small, infaunal prey. Since the degree of spatial variability in drilling intensity within any time bin can be extremely high, sometimes greater than the variability across consecutive time bins, temporal patterns in drilling predation can never be interpreted without having detailed knowledge of the nature of this spatial variability within a time bin.

Sex role similarity and sexual selection predict male and female song elaboration and dimorphism in fairy-wrens

Historically, bird song complexity was thought to evolve primarily through sexual selection on males, yet in many species both sexes sing. Previous research suggests competition for mates and resources during short, synchronous breeding seasons leads to more elaborate male songs at high latitudes. In contrast, we expect male-female song dimorphism and elaboration to be more similar at lower latitudes because longer breeding seasons and year-round territoriality yield similar social selection pressures in both sexes. However, studies seldom take both selective pressures and sexes into account. We examined song elaboration and sexual dimorphism in 15 populations of nine fairy-wren species (Maluridae), a Southern Hemisphere clade with female song. We compared song elaboration and sexual song dimorphism to latitude and life history variables tied to sexual and social selection pressures and sex roles. Our results suggest that song elaboration evolved in part due to sexual competition in males: male song variability was more positively correlated with temperate breeding and greater breeding synchrony than female song. We also found strong evidence that sex-role similarity contributed to male-female song similarity: male and female songs were shorter and more similar when parental care was more equal and when male survival was high. Contrary to Northern Hemisphere latitudinal patterns, songs were less dimorphic at higher, temperate latitudes. These results suggest that selection on song can be sex-specific, with male song elaboration favored in contexts coincident with sexual selection. However, selection pressures associated with sex-role similarity also appear to constrain sex specific song evolution and song dimorphism.

Global Patterns of Hottest, Coldest and Extreme Diurnal Variability on Earth

Most previous studies of extreme temperatures have primarily focused on atmospheric temperatures. Using 18 years of the latest version of the Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) data, we globally investigate the spatial patterns of hot and cold extremes as well as diurnal temperature range (DTR). We show that the world’s highest LST of 80.8 °C, observed in the Lut Desert in Iran and the Sonoran Desert in Mexico, is over ten degrees above the previous global record of 70.7 °C observed in 2005. The coldest place on Earth is Antarctica with the record low temperature of -110.9 °C. The world’s maximum DTR of 81.8 °C is observed in a desert environment in China. We see strong latitudinal patterns in hot and cold extremes as well as DTR. Biomes worldwide are faced with different levels of temperature extremes and DTR: we observe the highest zonal average maximum LST of 61.1 ± 5.3 °C in the deserts and xeric shrublands; the lowest zonal average minimum LST of -66.6 ± 14.8 °C in the Tundra; and the highest zonal average maximum DTR of 43.5 ± 9.9 °C in the montane grasslands and shrublands. This global exploration of extreme LST and DTR across different biomes sheds light on the type of extremes different ecosystems are faced with.