PRONOUNCED WITHIN‐INDIVIDUAL PLASTICITY IN SPERM MORPHOMETRY ACROSS SOCIAL ENVIRONMENTS

Sperm morphometry (i.e., size and shape) and function are important determinants of male reproductive success and are thought to be under stabilizing selection. However, recent studies suggest that sperm morphometry can be a phenotypically plastic trait, which can be adjusted to varying conditions. We tested whether different behavioral strategies in aggression between aggressive red and nonaggressive black males of the color polymorphic Gouldian finch (Erythrura gouldiae) can influence sperm morphometry. We show pronounced within‐individual phenotypic plasticity in sperm morphometry of male Gouldian finches in three different social environments. Both red and black males placed in intermediate to high competitive environments (high frequency of red males) increased the relative length of their sperm midpiece. By contrast, red males placed in low to intermediate competitive environments (higher frequency of black males) increased the length of the sperm flagellum. Significant changes in stress and sex steroid hormone levels (in response to the competitive environment) appear to influence sperm traits in red but not in black males, suggesting that changes in hormonal levels are not solely responsible for the observed changes in sperm morphometry. These findings imply that males can adjust sperm morphometry across social environments.     

Conservation of invertebrate biodiversity on a mountain in a global biodiversity hotspot,Cape Floral Region

Mountains present particular challenges for biodiversity conservation. Table Mountain is a significant mountain in a global biodiversity hotspot, the Cape Floristic Region. It has outstanding angiosperm diversity and endemism. Yet, aerial and foliage invertebrates in the area have been poorly studied, despite their importance as pollinators and predators. These plant and invertebrate assemblages are under great pressure from human disturbance. Aerial and foliage invertebrates were sampled with a range of techniques. Sites were chosen to make comparisons between vegetation structure and type, elevation and aspect. In total, 216 species from 63 families and 14 orders were recorded. Vegetation structure (fynbos or forest) and elevation were the most important environmental variables for both aerial and foliage invertebrates. Peak time for aerial invertebrate abundance was spring and summer in the fynbos and spring in the forests, while the foliage invertebrates showed very little seasonal variation. There was no correlation between the diversity of aerial and foliage invertebrates. When these results were compared with others on epigaeic invertebrates, it became clear that epigaeic and aerial invertebrates are not correlated, while epigaeic and foliage invertebrates were only partially correlated, but not sufficiently so to consider one as a reliable estimator of the other. The management pointer from this study is that sites at all elevations are vital for the conservation of biodiversity on Table Mountain. Both the aerial and epigaeic/foliage invertebrate assemblages will need to be monitored separately to maintain the mountain’s conservation status.     

The rehabilitation value of a small culturally significant island based on the arthropod natural capital

Small islands are particularly vulnerable to degradation by invasive species and often lack source populations to replace those lost during localized extinctions. Robben Island, a significant South African cultural heritage site, has a long history of anthropogenic impact. Introduced alien mammals and trees have resulted in numerous localized plant extinctions with their impact on arthropod biodiversity remaining unclear. We used Robben Island’s arthropod fauna as focal group to investigate the rehabilitation potential of this transformed island. Ground surface-living, foliage-inhabiting and flower-visiting arthropods were collected using five sampling techniques. Arthropod diversity was highest in the two ‘natural’ habitats compared to alien Eucalyptus plantations. Arthropod compositional diversity differed significantly between alien plantations and natural habitats. Nevertheless, a remarkable 17 % of all species were confined to plantations. However, when we corrected for the effect of rarity, only 15 species (4 %) were unique to alien plantations and all those identified to species level were either alien in origin or were widespread generalists only normally associated with transformed areas. This emphasizes the need to identify species that drive similarity indices to fully comprehend the conservation value of alien vegetation. Arthropods found in the remaining natural vegetation showed remarkable tolerance of long-term grazing pressures from introduced alien mammals. Only eight Orthoptera species were sampled, yet one was a rediscovery of a rare species and another a range extension. All indigenous species showed strong preferences for natural habitats. Thus, Robben Island could still hold conservation value if the natural habitats are rehabilitated and the Eucalyptus plantations removed.     

The hawk–dove game in a sexually reproducing species explains a colourful polymorphism of an endangered bird

The hawk–dove game famously introduced strategic game theory thinking into biology and forms the basis of arguments for limited aggression in animal populations. However, aggressive ‘hawks’ and peaceful ‘doves’, with strategies inherited in a discrete manner, have never been documented in a real animal population. Thus, the applicability of game-theoretic arguments to real populations might be contested. Here, we show that the head-colour polymorphism of red and black Gouldian finches (Erythrura gouldiae) provides a real-life example. The aggressive red morph is behaviourally dominant and successfully invades black populations, but when red ‘hawks’ become too common, their fitness is severely compromised (via decreased parental ability). We also investigate the effects of real-life deviations, particularly sexual reproduction, from the simple original game, which assumed asexual reproduction. A protected polymorphism requires mate choice to be sufficiently assortative. Assortative mating is adaptive for individuals because of genetic incompatibilities affecting hybrid offspring fitness, but by allowing red ‘hawks’ to persist, it also leads to significantly reduced population sizes. Because reductions in male contributions to parental care are generally known to lead to lower population productivity in birds, we expect zero-sum competition to often have wide ranging population consequences.     

Rockiness determines meso-scale conservation of butterflies in Afro-montane grassland

Understanding how and why certain species respond to various habitat resources can optimize conservation strategies. Furthermore, behaviour can contribute significantly to predicting the presence or absence of a species under certain habitat conditions. There is a measurable interaction between higher percentage rock exposure in a landscape and butterfly species richness and composition in montane grasslands. Here, we attempt to explain this interaction by measuring the behavioural responses of montane butterfly species to rock cover. The butterfly assemblage was observed across three increasing levels of rockiness in the landscape. At sites within each of these rockiness categories, we also sampled the different behavioural traits of the different species. We determined whether there were significant differences in behavioural traits among this assemblage in response to rockiness. We also identified the specific species which were responsible for driving differential behavioural responses under varying rock exposure in a landscape. The rockiest areas had significantly more behavioural events, and these behaviours were more often associated with direct utilization of rocks, and related to agonistic interaction. Certain butterfly species therefore use rocks as a utility habitat resource, in different ways, highlighting the importance of the resource-based habitat concept for conservation. As such, for butterfly conservation in these montane grasslands, emphasis is placed on including a rocky gradient in protected areas and conservation landscape designs.     

Enhancing flowering plant functional richness improves wild bee diversity in vineyard inter‐rows in different floral kingdoms

Wild bees are threatened by multiple interacting stressors, such as habitat loss, land use change, parasites, and pathogens. However, vineyards with vegetated inter‐rows can offer high floral resources within viticultural landscapes and provide foraging and nesting habitats for wild bees. Here, we assess how vineyard management regimes (organic vs. conventional; inter‐row vegetation management) and landscape composition determine the inter‐row plant and wild bee assemblages, as well as how these variables relate to functional traits in 24 Austrian and 10 South African vineyards. Vineyards had either permanent vegetation cover in untilled inter‐rows or temporary vegetation cover in infrequently tilled inter‐rows. Proportion of seminatural habitats (e.g., fallows, grassland, field margins) and woody structures (e.g., woodlots, single trees, tree rows) were used as proxies for landscape composition and mapped within 500‐m radius around the study vineyards. Organic vineyard management increased functional richness (FRic) of wild bees and flowering plants, with woody structures marginally increasing species richness and FRic of wild bees. Wild bee and floral traits were differently associated across the countries. In Austria, several bee traits (e.g., lecty, pollen collection type, proboscis length) were associated with flower color and symmetry, while in South African vineyards, only bees’ proboscis length was positively correlated with floral traits characteristic of Asteraceae flowers (e.g., ray–disk morphology, yellow colors). Solitary bee species in Austria benefitted from infrequent tillage, while ground nesting species preferred inter‐rows with undisturbed soils. Higher proportions of woody structures in surrounding landscapes resulted in less solitary and corbiculate bees in Austria, but more aboveground nesting species in South Africa. In both countries, associations between FRic of wild bees and flowering plants were positive both in organic and in conventional vineyards. We recommend the use of diverse cover crop seed mixtures to enhance plant flowering diversity in inter‐rows, to increase wild bee richness in viticultural landscapes.     

Frequency-dependent physiological trade-offs between competing colour morphs

Evolutionary theory suggests that alternative colour morphs (i.e. genetically controlled phenotypes) may derive similar fitness under frequency-dependent selection. Here we experimentally demonstrate opposing effects of frequency-dependent social environments on plasma hormone levels (testosterone and corticosterone) and immune function between red- and black-headed male morphs of the Gouldian finch (Erythrura gouldiae). Red-headed males are highly sensitive to changes in the social environment, especially towards the relative density of their own aggressive morph, exhibiting high stress responses and immunosuppression in socially competitive environments. In contrast, the non-aggressive black-headed males follow a more passive strategy that appears to buffer them against social stresses. The differential effect of hormones on aggressive behaviour and immune performance reinforces the contrasting behavioural strategies employed by these colour morphs, and highlights the importance of the social environment in determining the individual basis of behavioural and physiological responses.     

POSTZYGOTIC GENETIC INCOMPATIBILITY BETWEEN SYMPATRIC COLOR MORPHS

Alternative genetically determined color morphs within a population or species are believed to successfully interbreed within a population. However, the occurrence of prezygotic or ecological selection in a number of polymorphic systems may lead to nonrandom mating and prevent genetic morphs from fully interbreeding. Here we show that postzygotic incompatibility significantly limits gene flow between the sympatric red and black color morphs of the Gouldian finch ( Erythrura gouldiae ). Using a balanced within-female experimental design, in which individuals were forced to breed in pure and mixed morph crosses, we found large inviability effects (>30%) in offspring resulting from genetically mixed genotypes. The consistent mortality effects across different stages of development (e.g., prehatching, juvenile, adulthood), unconfounded by environmentally derived parental effects or social environments, reveal an underlying genetic incompatibility between different genotypes. Furthermore, mortality in mixed morph genotypes was particularly severe (43.6%) for the heterogametic sex (daughters), which is consistent with Haldane's rule predicted for postzygotic incompatibilities between hybridizing species. This significant, but incomplete, postzygotic isolation suggests that the sympatric morphs may represent transient stages in the speciation–hybridization process.     

Sexual selection of multiple handicaps in the red-collared widowbird: female choice of tail length but not carotenoid display

Although sexual selection through female choice explains exaggerated male ornaments in many species, the evolution of the multicomponent nature of most sexual displays remains poorly understood. Theoretical models suggest that handicap signaling should converge on a single most informative quality indicator, whereas additional signals are more likely to be arbitrary Fisherian traits, amplifiers, or exploitations of receiver psychology. Male nuptial plumage in the highly polygynous red-collared widowbird (Euplectes ardens) comprises two of the commonly advocated quality advertisements (handicaps) in birds: a long graduated tail and red carotenoid coloration. Here we use multivariate selection analysis to investigate female choice in relation to male tail length, color (reflectance) of the collar, other aspects of morphology, ectoparasite load, display rate, and territory quality. The order and total number of active nests obtained are used as measures of male reproductive success. We demonstrate a strong female preference and net sexual selection for long tails, but marginal or no effects of color, morphology, or territory quality. Tail length explained 47% of male reproductive success, an unusually strong fitness effect of natural ornament variation. Fluctuating tail asymmetry was unrelated to tail length, and had no impact on mating success. For the red collar, there was negative net selection on collar area, presumably via its negative relationship with tail length. None of the color variables (hue, chroma, and brightness) had significant selection differentials, but a partial effect (selection gradient) of chroma might represent a color preference when tail length is controlled for. We suggest that the red collar functions in male agonistic interactions, which has been strongly supported by subsequent work. Thus, female choice targets only one handicap, extreme tail elongation, disregarding or even selecting against the carotenoid display. We discuss whether long tails might be better indicators of genetic quality than carotenoid pigmentation. As regards the evolution of multiple ornaments, we propose that multiple handicap signaling is stable not because of multiple messages but because of multiple receivers, in this case females and males.     

Genomic affinities in Arachis section Arachis (Fabaceae): molecular and cytogenetic evidence

Section Arachis is the largest of nine sections in the genus Arachis and includes domesticated peanut, A. hypogaea L. Most species are diploids (x=10) with two tetraploids and a few aneuploids. Three genome types have been recognized in this section (A, B and D), but the genomes are not well characterized and relationships of several newly described species are uncertain. To clarify genomic relationships in section Arachis, cytogenetic information and molecular data from amplified fragment length polymorphism (AFLP) and the trnT-F plastid region were used to provide an additional insight into genome composition and species relationships. Cytogenetic information supports earlier observations on genome types of A. cruziana, A. herzogii, A. kempff-mercadoi and A. kuhlmannii but was inconclusive about the genome composition of A. benensis, A. hoehnei, A. ipaensis, A. palustris, A. praecox and A. williamsii. An AFLP dendrogram resolved species into four major clusters and showed A. hypogaea grouping closely with A. ipaensis and A. williamsii. Sequence data of the trnT-F region provided genome-specific information and showed for the first time that the B and D genomes are more closely related to each other than to the A genome. Integration of information from cytogenetics and biparentally and maternally inherited genomic regions show promise in understanding genome types and relationships in Arachis.