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Protected areas are of paramount relevance to conserving wildlife and ecosystem contributions to people. Yet, their conservation success is increasingly threatened by human activities including habitat loss, climate change, pollution, and species overexploitation. Thus, understanding the underlying and proximate drivers of anthropogenic threats is urgently needed to improve protected areas' effectiveness, especially in the biodiversity-rich tropics. We addressed this issue by analyzing expert-provided data on long-term biodiversity change (last three decades) over 14 biosphere reserves from the Mesoamerican Biodiversity Hotspot. Using multivariate analyses and structural equation modeling, we tested the influence of major socioeconomic drivers (demographic, economic, and political factors), spatial indicators of human activities (agriculture expansion and road extension), and forest landscape modifications (forest loss and isolation) as drivers of biodiversity change. We uncovered a significant proliferation of disturbance-tolerant guilds and the loss or decline of disturbance-sensitive guilds within reserves causing a "winner and loser" species replacement over time. Guild change was directly related to forest spatial changes promoted by the expansion of agriculture and roads within reserves. High human population density and low nonfarming occupation were identified as the main underlying drivers of biodiversity change. Our findings suggest that to mitigate anthropogenic threats to biodiversity within biosphere reserves, fostering human population well-being via sustainable, nonfarming livelihood opportunities around reserves is imperative.

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Insect life cycles are short-term and therefore sensitive to immediate changes triggered by climate, vegetation structure, or land use management; hence, the insect populations shape the communities and functional relationships in tropical forests. In this study, we hypothesized that seasonal variations of the dipteran families respond in different ways to changes of weather conditions, thereby affecting their population dynamics. In a one-hectare plot, we surveyed the fly community inhabiting the understory of a Neotropical rainforest. Over a yearly cycle, we used three Malaise traps operated continuously for 365 days and recorded a total of 68,465 fly specimens belonging to 48 families of Diptera, 15 of which were most abundant, accounting for 99.2% of all sampled individuals. The results of the trapping frequency indices (TFIs) exhibited significant population fluctuations in 12 of the 15 most abundant families, which were particularly correlated with temperature or precipitation. Based on such variations, we identified four seasonal patterns as follows: (i) Spring-Autumn bimodal pattern (Cecidomyiidae, Sciaridae, Phoridae, Stratiomyidae); (ii) Spring pattern (Mycetophilidae, Dolichopodidae, Ceratopogonidae); (iii) Autumn pattern (Chironomidae, Psychodidae); (iv) Winter pattern (Empididae, Tipulidae, Ditomyiidae). From a functional perspective, we found the prevalence of families with saprophagous larvae, in addition to phytophagous, fungivores, and predacious. Our results suggest a key role played by the Diptera community on structuring the functional clusters, both in terms of taxonomic composition and on seasonal shifts of abundance, thus influencing the dynamic processes of nutrient cycling in the understory.

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Seed priming increases the vigor of seeds and seedlings through metabolic and biochemical processes occurring during controlled hydration, followed by dehydration. In the field, seeds are exposed to hydration-dehydration events in and on the soil after dispersal, as in seed priming. Nevertheless, seed priming has been sparsely tested on desiccation-sensitive seeds, which are vulnerable to climate change effects. We evaluated the effect of two priming methods on seeds from two tropical rainforest species: Cupania glabra and Cymbopetalum baillonii. For hydropriming, the seeds were fully hydrated and then dehydrated to three dehydration levels. For natural priming, the seeds were buried for 12 days in either closed forest or forest gap. Primed seeds were sown in 1% agar medium and placed in an environmental chamber. The growth of the seedlings from the highest germination priming treatments was evaluated for 1 year in the field. Our results showed that for C. glabra and C. baillonii, hydroprimed seeds varied in their germination response, depending on the degree of their dehydration. However, for C. baillonii, hydropriming seems to invigorate seeds, compared to non-imbibed seeds of the same dehydration level. Natural priming increased germination speed in both species without any difference between closed forest and forest gap. Moreover, seeds with natural priming had a higher final germination percentage than seeds with hydropriming. Seedlings from seeds with natural priming showed a higher growth rate than the controls in both species, whereas hydropriming produced a similar effect in C. glabra. Both priming methods could be used for restoration practices with the studied species, natural priming being a novel method. The ecological implications of priming in desiccation sensitive seeds are discussed in this study.

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Dung beetles are secondary seed dispersers, incidentally moving many of the seeds defecated by mammals vertically (seed burial) and/or horizontally as they process and relocate dung. Although several studies have quantified this ecological function of dung beetles, very few have followed seed fate until seedling establishment, and most of these have focused on the effects of seed burial. We know very little about the effects of horizontal seed movement by dung beetles, though it is generally assumed that it will affect plant recruitment positively through diminishing seed clumping. The objective of our study was to assess the effects of dung beetle activity on the spatial distribution of seeds and seedlings, and on the probability of seedling establishment. In a tropical rainforest in Mexico we carried out two complementary field experiments for each of two tree species (Bursera simaruba and Poulsenia armata), using seeds experimentally imbedded in pig dung and recording their fate and spatial location over time. For both species, dung beetle activity reduced the spatial clumping of seeds and seedlings; however, it did not increase the probability of seedling establishment. We discuss the context- and species-specificity of the combined effects of horizontal and vertical dispersal of seeds by dung beetles, and the need to quantify long-term seedling fates to more accurately determine the effects of seed movement by dung beetles on plant recruitment.

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Although there is a large diversity of plant species with extrafloral nectaries, histological detail of these glands is poorly documented in tropical rain forest species. We characterized extrafloral nectaries using digital photographs, scanning electron microscopy and histological methods for eight plant species belonging to the Costaceae, Euphorbiaceae, Malvaceae and Salicaceae. To our knowledge, there are no previous reports on the structure of extrafloral nectaries for these species. Croton species exhibited reddish extrafloral nectaries on the petioles, surrounded by starshaped trichomes. Cnidoscolus multilobus and Omphalea oleifera showed green, elevated, extrafloral nectaries at the peduncle; C. multilobus showed abundant secretory tissue; O. oleifera revealed numerous cells with calcium oxalate crystals. Heliocarpus species showed extrafloral nectaries distributed at the base of the blade and possesses glands in the center of the extrafloral nectary surrounded by a series of parenchymatic cells. Pleuranthodendron lindenii has two extrafloral nectaries at the base of the leaves. Costus scaber has a hollow-type extrafloral nectary on the red-colored bracts of the inflorescence; nectar cavity is found in the center area of each bracts located on a yellow line. The extrafloral nectaries described in this study exhibited different morphologies and histological structures involved in the secretion of extrafloral nectar that could be related to biotic defenses, primarily by attracting ants.

Embora exista uma grande diversidade de espécies de plantas com nectários extraflorais, detalhes histológicos destas glândulas ainda é pouco documentado para espécies tropicais. Nós caracterizamos nectários extraflorais usando fotografias digitais, microscopia eletrônica de varredura e métodos histológicos para oito espécies de plantas das famílias Costaceae, Euphorbiaceae, Malvaceae e Salicaceae. Para nosso conhecimento, não há relatos anteriores sobre a estrutura dos nectários extraflorais para as espécies estudadas. Espécies de Croton exibiram nectários extraflorais avermelhadas nos pecíolos, rodeados por tricomas em forma de estrela. Cnidoscolus multilobus e Omphalea oleifera apresentaram nectários extraflorais verdes e elevados nos pedúnculos; C. multilobus apresenta tecido secretor abundante enquanto que O. oleifera apresentou numerosas células com cristais de oxalato de cálcio. Espécies de Heliocarpus apresentaram nectários extraflorais distribuídos na base da lâmina e possuíam glândulas no centro do nectário rodeadas por uma série de células de parênquima. Pleuranthodendron lindenii apresentou dois nectários extraflorais na base das folhas. Costus scaber apresenta um nectário extrafloral do tipo oco nas brácteas avermelhadas da inflorescência, e a cavidade do nectário se encontra na área central de cada bráctea localizados em uma linha amarela. Os nectários extraflorais descritos neste estudo apresentaram morfologia e estruturas histológicas diferentes envolvidas na secreção de néctar extrafloral que poderia estar relacionado com defesas bióticas, principalmente atraindo formigas.

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