Acta Oecologica-International Journal of Ecology最新文献

A female-biased clutch sex ratio is selected under local mate competition since it reduces competition between male sibs and provides extra mating opportunities for sons. Theoretical models predict that the brood sex ratio of fig wasps becomes less female-biased as the number of wasps laying eggs in the same fig increases. Empirical data have demonstrated that pollinator females lay most of their male eggs first, followed by the female ones in an oviposition bout (males first rule). As oviposition sites are limited in the fig, the brood sex ratio is positively correlated with the number of wasps laying eggs. To understand the strategy of sex ratio adjustment of Sycobia hodites, a non-pollinating fig wasp associated with Ficus benjamina, we compared observed and simulated data. The female wasp starts oviposition shortly after landing on the fig. This process involves the insertion of the ovipositor through the fig surface and into the flower's ovary via the stigma/style. The brood sex ratio of S. hodites did not significantly correlate with the fig brood size. Brood simulations supported the notion that the sex ratio of S. hodites is automatically determined by the male-first rule, involving no control by the mothers. The simulation model best fitting empirical data considered that: (1) females lay few eggs per fig (six or less) and distribute their eggs among several figs, and (2) the probability of an egg producing a male wasp decreases with its position in the egg sequence. Empirical and simulated data showed a wide variation in both brood size and sex ratio, suggesting that selection for an optimal clutch sex ratio is possibly weak. We argue that when selective pressure for sex ratio adjustment is weak, evolution favors male polymorphism as a strategy to cope with mate competition.

Plant odours are central for pollinator attraction. This is particularly true in obligate brood site pollination mutualisms. However, we know little about the evolution of olfactory signalling in these mutualisms. Here, we investigate geographic variation of floral odour in the obligate host-specific brood site pollination mutualism between Ficus hirta and its specialised pollinators. Floral scent samples from nine locations in China were collected using head-space adsorption and were analysed by gas chromatography-mass spectrometry. We evidence progressive geographic divergence of floral odours. The pattern of variation fits plant genetic structure for neutral genes but differs from pollinating insect structuring into species and populations. In our study system, the geographic variation of receptive floral odour presents a pattern that is not distinguishable from neutral drift. The variation is not canalised by the insects. We propose that this pattern characterises obligate brood site pollination mutualisms in which pollinators are host specific and dispersal of plant and insect is limited. Insects with their short generation times and large population sizes rapidly track any chance variation in host receptive inflorescence odours. Plants are the drivers and insects the followers. The source of the geographic variation in floral odours can be genetic or phenotypic in response to local conditions. Strict sense plant-insect co-evolution is not involved. In contrast, previous results on another Ficus-pollinating wasp association suggest that stabilising selection could be at work in more dispersive systems.

Semideciduous Seasonal Forest is a phytophysiognomy of Atlantic Forest with high plant richness but low representativeness in few remnants areas in different successional stages. The assessment of the degree of conservation of those areas helps to indicate whether there is a need for taking strategies to favor forest succession. Thus, the aim of this study was to identify litterfall and its nutrient content, accumulated litter biomass on topsoil, leaf litter decomposition, and topsoil (0–10 cm) chemical attributes as possible indicators of successional stages in areas of Seasonally Semideciduous Forest. We collected available information in literature on CAPES Portal and Google Scholar (May/2021 to February/2022) for Pinheiral municipality, State of Rio de Janeiro, Brazil, which were evaluated by multivariate analysis. Accumulated litter biomass, nutrient content (N, P, K) in total litterfall, pH and P availability in topsoil, leaf litter decomposition constant, and half-life time of leaf litter were the most sensitive attributes to indicate the successional stage in the study area, according to Principal Component Analysis. This multivariate analysis indicated that areas in early successional stage were associated with higher values of leaves contribution, half-life of leaf litterfall, contents of Ca and K in total litterfall, whereas areas in middle successional stage were associated with higher values of pH, total organic carbon, exchangeable Ca²⁺, K⁺, and Mg⁺, sum of bases and cation exchange capacity, and lower values of extractable acidity and exchangeable Al³⁺ in the topsoil. Areas in advanced stages of succession were associated to higher values of total litterfall and its nutrient content (N, K, Mg), accumulated litter biomass, available P in topsoil, and leaf litter decomposition constant. The Cluster multivariate analysis revealed that the areas in advanced successional stage presented high dissimilarity in relation to the areas in early and middle successional stage.

Coarse woody debris (CWD) and litter are important habitats and nutrient sources for soil fungi. However, the roles of CWD and litter in maintaining soil fungal community composition and function at different successional stages remain unknown. Therefore, we collected soils beneath the CWD and litter from a subalpine forest successional series: shrubs, deciduous broadleaf, broadleaf-conifer mixed, mid-succession coniferous, mature coniferous, and over-mature coniferous forests in the subalpine forest region. The diversity, composition, and functional guilds of the soil fungal communities beneath the CWD and litter layer were analyzed using ITS (Internal Transcribed Spacer) sequencing. The CWD significantly changed the composition and functional guilds of the soil fungal communities in the same successional series. However, there was no significant difference in the soil fungal alpha diversity between the two microhabitats at the same successional stage. Notably, the soil beneath the litter layer had more abundant plant pathogens and mycorrhizal fungi, whereas the soil beneath CWD was enriched mainly with saprotrophic and ectomycorrhizal fungi. The relative abundance of plant pathogens and mycorrhizal fungi was significantly related to the soil pH and the CWD stock. In addition, soil nitrogen, carbon, and the C: N ratio were key driving factors for the taxonomic composition and functional guilds of the soil fungal community. In conclusion, CWD exerts critical functions in nursing soil fungal diversity and maintaining the structure and function of soil fungal community mainly due to CWD decomposes slowly, increases soil heterogeneity, and provides with microhabitats and substrates for fungi in a longer term.

In addition to physiological functions, sticky plant trichomes perform a variety of anti-herbivory functions, such as deterring invertebrate and mammalian herbivores, and attracting the natural predators of stuck arthropods by providing them with immobilized prey. However, since the adaptive value of sticky glands has only been studied in a small fraction of trichrome-bearing plant species, other functions of these structures may yet be discovered. Several hemiparasitic plants, which obtain nutrients by both photosynthesis and from the roots of other plants, bear dense glandular trichomes on their aboveground parts. Field observations of the alien hemiparasitic plant Parentucellia viscosa were conducted in central Japan. The plants colonized a sparsely vegetated riverbank and gradually increased in number over time. The glandular trichomes on the plants not only entrapped small insects, but also grass seeds. It is thus possible that various sticky hemiparasitic plants, including P. viscosa, may intercept and capture the dispersed seeds of other plants, ensuring that their own seeds germinate in the same vicinity as those of the dispersing hostplant seeds in the following season. In so doing, P. viscosa may provision future juvenile plants with potential hosts. This scenario may be restricted to the early colonizing phase on plantless areas of disturbed soil. The seed-intercepting function of the glandular trichomes may act in conjunction with direct and indirect anti-herbivore defenses, and lower the dispersal of seeds of wind-borne plants in the vicinity beyond the reach of this hemiparasite.

Species boundaries are maintained by limitations on gene flow between taxa. In flowering plants pollinator specificity can strongly influence gene flow patterns and facilitate speciation. Fig trees are species rich and ecologically significant plants. It was once believed that each species had its own unique pollinator fig wasp, but numerous exceptions are now known. The dioecious Ficus deltoidea complex is distributed across southern South-East Asia with 13 recognised varieties of uncertain status, seven of which are found in Peninsular Malaysia. We investigated the host preferences of one of their Blastophaga pollinators, reared from the epiphytic F. deltoidea var. angustifolia. Our series of experimental manipulations using free-flying fig wasps and figs on host trees showed that male figs were preferred, that only their natal variety was attractive and that pollinators only dispersed from their natal trees if no suitable figs were present there. Fig wasps can only reproduce in male hosts, so preferred entry to male figs has clear advantages for them, as does their reluctance to disperse from natal trees. This behaviour is likely to reduce seed set on female plants, with potential consequences for host population dynamics. The extreme specificity of the Blastophaga sp. suggests gene flow between varieties of F. deltoidea is low or absent and that different varieties may be different biological species.

We tested the hypothesis that abiotic predictors, both influence α and β-diversity of macroinvertebrate communities in the phytotelmata of the terrestrial bromeliad, Vriesea philippocoburgii. Macroinvertebrates were sampled in 58 bromeliads in a restinga in Brazil and estimated both the α and β-diversity in each bromeliad, and then partitioning them into nestedness and turnover. We then used Generalized Linear Models and partial Mantel tests to identify which environmental factors predict these diversity components for the macroinvertebrate communities. The size of the plant positively influenced α-diversity, whereas light intensity strongly influenced β-diversity. Both components were influenced by organic matter. Plants exhibiting large differences in values of organic matter and light intensity had different macroinvertebrate communities. Furthermore, bromeliad systems exhibit high β-diversity values governed by turnover. Our findings demonstrate the importance of considering α and β-diversities in studies that assess the diversity patterns of aquatic macroinvertebrates and suggest that environmental changes that modify the structure of aquatic macroinvertebrate communities could have impacts on ecosystem processes.

The susceptibility of a plant community to invasion is influenced by multiple factors including the characteristics of the invading species and the invaded environment but how road presence and woodland type affect invasibility in woodlands invaded by Lantana camara (hereafter, lantana) in southern Africa is not well known. We identified roads adjacent to miombo, Vachellia (hereafter, vachellia) and mixed woodlands. Parallel to each road, we laid two transects (200 × 30 m) and replicated them twice, one adjacent to the road and another in the interior. In each transect, we laid 5 plots (30 × 20 m), making a total of 60 plots (3 woodland types x 2 transects x 2 replicates x 5 plots). Our sampling plan yielded six woodland clusters: roadside vachellia, interior vachellia, roadside miombo, interior miombo, roadside mixed and interior mixed. Road presence increased invasibility in all clusters but was more pronounced in less diverse miombo and vachellia than in more diverse mixed woodland. Interior mixed woodland was 1.4 and 1.8 times more diverse than interior miombo and interior vachellia woodlands, respectively; whereas roadside mixed woodland was twice more diverse than roadside miombo and roadside vachellia. Invasibility in the interior mixed woodland was 19% and 24% lower than in the interior miombo and interior vachellia, respectively; whereas in the roadside mixed woodland, it was 19% and 21% lower than in roadside miombo and roadside vachellia, respectively. We found a negative diversity-invasibility relationship in all clusters. Vachellia woodlands had significantly higher soil C, N, P and K concentrations than miombo but were equally susceptible to lantana invasion. Collectively, our findings suggest that high diversity rather than low soil nutrient status might be more important in hindering plant invasion. We emphasize the importance of conserving native diversity in roadside habitats to reduce the success of invading plant species.

Fig (Moraceae: Ficus) species host vast communities of organisms that are bound together by complicated ecological networks that have influenced community structure and dynamics over evolutionary timescales. Much attention has been paid to the mutualism between figs and their specialized pollinating fig wasps, as well as with often antagonistic non-pollinating fig wasps. Equally ubiquitous to fig systems, but much less understood are the multitude of nematode groups that have independently evolved obligate associations with pollinating fig wasps and proliferate inside fig syconia. In this review we describe what is currently known (and unknown) about these numerous and increasingly studied nematode taxa and how they interact with the fig systems they inhabit. We identify the groups that are currently understood to associate with fig pollinators and outline their known species distributions and evolutionary history, where possible. Special attention is paid to the life history of these nematode groups, especially which features of nematode biology are generalizable across groups and what idiosyncratic peculiarities exist within individual genera. We outline key biological features including host choice, dispersal, disembarkation, diet, mating, and proliferation within figs. We address biological conundrums that have been raised following observational work such as, why do nematodes sometimes infect the wrong host? What adaptations were required for nematodes to successfully adapt and coexist with figs and their pollinators for millions of years? How do nematodes overcome the constraints of low mating group size? Finally, we outline key considerations, gaps in the knowledge, and limitations to expand this field forward towards promising areas of future research. Through better understanding of fig nematodes, we stand to not only know more about Ficus communities, but also more about the evolution and maintenance of interspecific interactions, development, adaptation, and co-evolution in general.

Rare and cryptic species require effective monitoring methods in order to track populations over time. Monitoring surveys utilizing artificial refugia are an increasingly applied tool for detecting herpetofauna; yet for many species, limited information is available on the factors that influence optimal detectability. Most monitoring programs utilize only one type of artificial refuge. This approach has limitations as it may overlook the dynamic habitat needs of some species, with different refugia required under different conditions. Here we investigate whether using two different types of artificial refugia could maximize overall detection of the endangered Monaro grassland earless dragon Tympanocryptis osbornei by providing refugia that match habitat use. Tympanocryptis osbornei is a grassland specialist endemic to the Monaro Plains of southern NSW which occurs within a fragmented and altered agricultural landscape. Artificial refuge habitat in the form of customized replica ‘spider’ tubes and concrete roof tiles were utilized to infer the highest detection probability when compared to traditional rock rolling techniques. We found tubes to be more successful than tiles (mean: 0.021, 0.010–0.037 95% Bayesian credible interval (BCI) vs mean: 0.0096, 0.0045–0.018 95% BCI). However, this was dependent on air temperature, as tiles became more effective between 25 and 30 °C when dragons were more likely to be using surface shelters. Artificial refugia on a transect level (12 tubes and 12 tiles) had the greatest detection probability (mean: 0.11, 0.04–0.23 95% BCI) compared to individually checked objects. Our results identify the best current methods and conditions to detect T. osbornei and provide insights into additional considerations for optimizing survey efforts, timing, and detectability for other small reptiles in temperate climates. We recommend a combination of artificial refugia be considered in future surveys for cryptic reptiles.