Bromeliads provide shelter against fire to mutualistic spiders in a fire‐prone landscape

1. A key challenge in the study of mutualistic interactions is understanding sources of variation that strengthen or weaken these interactions. In spider–plant mutualisms, spiders benefit plants by improving plant nutrition and protecting plants from herbivory. Although the benefits of plants to spider growth and survival are often claimed, they are rarely demonstrated. 2. In this study, empirical evidence is provided that bromeliads (Bromelia balansae, Bromeliaceae) are essential for the resilience of the mutualistic bromeliad‐living jumping spider populations (Psecas chapoda, Salticidae) after a fire event, sheltering spiders from the heat of the flames. 3. Spider populations were compared before and after a natural fire event and it was shown that spiders of different ages survived the fire. The survival of such individuals allowed the population of P. chapoda spiders to recover rapidly, returning to pre‐fire levels in 5 months. 4. Bromeliads reduced the susceptibility of P. chapoda spiders to burning, and this mutualistic relationship contributed to the resilience of the spider population after a fire event. It is suggested that frequent fires in fire‐prone landscapes may have strengthened this spider–plant relationship, contributing to the maintenance and evolution of this association.     

Sexual dimorphism and interpopulation differences in lizard hind limb length: locomotor performance or chemical signalling?

Intraspecific variation in morphology has often been related to fitness differences through its effects on performance. In lizards, variation in hind limb length can be shaped by natural selection for increased locomotor performance, sexual selection on the number or size of femoral pores involved in chemical signalling, or both. Here, we analyse the selective forces involved in sexual dimorphism and differences in hind limb length between two populations of Psammodromus algirus living at different elevation. Males were more robust and had longer hind limbs and limb segments than females, and low‐elevation lizards had longer limbs than high‐elevation lizards. However, differences in locomotor performance were small and non‐significant, making natural selection for faster runs an unlikely explanation for the observed pattern. On the other hand, males had more femoral pores than females, and lizards had more pores at lower elevation, although the difference was significant only for males (which invest more in chemical signalling). In males, the number of pores, which remains constant along a lizard's life, was not correlated with hind limb length. However, femur length was positively correlated with mean pore size, allowing low‐elevation males to have larger than expected pores, which could increase the effectiveness with which they spread their signals in a dry and warm habitat where chemicals become volatile rapidly. Also, saturation of the sexual coloration of the head was higher for low‐elevation males, suggesting that sexual selection pressures may be more intense. Overall, our results indicate that sexual selection plays a significant role in shaping intraspecific variation in hind limb length. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 318–329.     

Genetic diversity in Atlantic Forest trees: fragmentation effects on Astronium graveolens (Anacardiaceae) and Metrodorea nigra (Rutaceae), species with distinct seed dispersal strategies

We explore the genetic structure and variability in autochorous Metrodorea nigra (Rutaceae) and anemochorous Astronium graveolens (Anacardiaceae), two species affected by deforestation in the Atlantic Forest of Brazil. The effects of deforestation and the depletion of the habitat within the remaining patches of forest are evaluated by comparing the variability between saplings and adults of each of these two species. The results indicate that the depletion of forest land and the deteriorating condition of the remaining fragments of forest may reduce the level of endogamous breeding in wind‐dispersed species. In autochorous species, the fragmentation of forest land has less notable effects on genetic attributes, but pollen flow could be decreased as a result of the reduced number of insects flying between the forest remnants. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 326–336.     

Species limits and hybridization zones in Icterus cayanensis–chrysocephalus group (Aves: Icteridae)

One of the best examples of differentiation and hybridization among South American passerine birds is exhibited by Icterus cayanensis (Epaulet Oriole) and Icterus chrysocephalus (Moriche Oriole). Icterus chrysocephalus is a monotypic species restricted to northern South America. Icterus cayanensis is a polytypc species that ranges from Suriname and French Guyana to northern Argentina. Five subspecies are recognized to I. cayanensis. Hybrid zones are known between I. cayanensis and I. chrysocephalus as well as between subspecies of I. cayanenis, even though character variation has never been adequately assessed and mapped. Although molecular data support the hypothesis that I. cayanensis and I. chrysocephalus form a monophyletic group, they do not support the species limits currently recognized within this group. We analysed the geographic variation of plumage characters along the range of this group to map the geographic variation of individual plumage characters and identify the populations that have uniform phenotypic character expression and therefore represent genuine phylogenetic species. We also used molecular data to investigate the phylogenetic relationships among these species. Geographic variation of plumage characters, habitat preferences and molecular data identified four species within I. cayanensis–chrysocephalus clade: an Amazonian species group, formed by I. cayanensis and I. chrysocephalus and a Southern species group composed of I. pyrrhopterus and I. tibialis. The Amazonian species are separated by a relatively narrow hybrid zone along the Amazon valley, whereas the Southern species are separated by a hybrid zone that is larger than the ranges of the two species individually. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 583–597.     

Divide to conquer: a complex pattern of biodiversity depicted by vertebrate components in the Brazilian Atlantic Forest

The identification of northern and southern components in different vertebrate species led researchers to accept a two‐component hypothesis for the Brazilian Atlantic forest (BAF). Nevertheless, neither a formal proposal nor a meta‐analysis to confirm this coincidence was ever made. Our main objective here was therefore to systematically test in how many vertebrate components the BAF could be divided by analysing existing empirical data. We used two approaches: (1) mapping and comparing the proposed areas of vertebrate endemism in the BAF and (2) analysing studies mentioning spatial subdivisions in distinct forest‐dependent vertebrates within the biome, by the use of panbiogeography. The four large‐scale endemism area components together with the six small‐scale panbiogeographical ones allowed the definition of three BAF greater regions, subdivided into nine vertebrate components, latitudinally and longitudinally organized. Empirical time estimates of the diversification events within the BAF were also reviewed. Diversification of these vertebrates occurred not only in the Pleistocene but also throughout the Miocene. Our results confirm the BAF's complex history, both in space and time. We propose that future research should be small‐scale and focused in the vertebrate components identified herein. Given the BAF's heterogeneity, studying via sections will be much more useful in identifying the BAF's historical biogeography. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

Seed dispersal and population structure in Vriesea gigantea,a bromeliad from the Brazilian Atlantic Rainforest

Seed dispersal, population structure and the mating system of plant species can have great consequences on the genetic structure of populations. Vriesea gigantea is a bromeliad from southeastern Brazil which is self‐compatible and pollinator dependent for fruit set. Its populations are fertile in terms of the production of flowers, pollen, fruits and seeds. To assess the importance of seed supply for gene flow, colonization and distribution of adult individuals, the seed dispersal and population structure of V. gigantea were studied. Seeds are dispersed over short distances; most seeds land close to the mother plant. This pattern coincides with the reported aggregate distribution of bromeliad seedlings. Population structure results showed high seedling recruitment, because 51.3% developed into adults, although few juveniles reached this stage. This result is different from that for other bromeliad species from different habitat conditions. Seed dispersal and population structural patterns are consistent with previous molecular studies, revealing that V. gigantea populations are genetically structured, with low gene flow and a moderate outcrossing rate. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 317–325.     

The role of capacitance in the water balance of Andean giant rosette species

Abstract Pith water storage capacity and its role in plant-water relations were studied in seven giant rosette species of the genus Espeletia from the Venezuelan Andes. Readily available water from the pith was calculated to be capable of sustaining mean transpiration for up to 2.5 h. The relative importance of water stored in the pith, however, differed among species. The species that grow in the higher and colder environments tended to have a greater capacitance than the species that grow in the lower and less extreme environments. The pith volume per unit leaf area (PV/LA) was found to be a good indicator of the relative water storage capacity of the adult individuals of each species. Diurnal fluctuations in leaf water potential were not as pronounced in the species with higher PV/LA values. The species-specific PV/LA was highly correlated with the leaf turgor loss point and with the total resistance to water flow from soil to leaves. These results suggested that species-specific capacitance in the genus Espeletia is a response to temperature-limited soil water availability and that cold tropical environments with frequent subfreezing temperatures tend to select for high water storage capacity in giant rosette plants.     

Contrasting engineering effects of leaf‐rolling caterpillars on a tropical mite community

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Inbreeding depression in Vriesea gigantea,a perennial bromeliad from southern Brazil

Inbreeding depression is a reduction of fitness in the progeny of closely related individuals and its effects are assigned to selfing or biparental inbreeding. Vriesea gigantea is a self‐compatible bromeliad species distributed in the Brazilian Atlantic rainforest and habitat destruction and fragmentation and collection have decreased the natural populations. We aim to describe the occurrence of inbreeding depression (δ) in three natural populations of V. gigantea and to correlate this phenomenon with previous studies of fertility, genetic diversity, population genetic structure, gene flow, mating system and seed dispersal in this species. Fifty‐four adult plants were sampled and 108 flowers were used for pollination treatments (selfing, outcrossing and control). For adult plants, we analysed plant and inflorescence height, flower numbers and seed set. In the progenies, evaluated parameters included seed germination and seedling survival rate. The results indicated low to moderate levels of inbreeding depression in V. gigantea (δ = 0.02 to 0.39), in agreement with molecular data from a previous study. Vriesea gigantea populations tolerate some degree of inbreeding, which is consistent with previous results on fertility, mating system, genetic diversity and gene flow. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 312–319.