Aims Our main aims are to test how: (1) different nurse species modulate the early establishment of multiple beneficiary species in a degraded area; (2) the intensity and direction of species‐specific interactions between nurse and beneficiary species change during beneficiary ontogeny. Location A shrubby Caatinga forest at Petrolina, northeast Brazil, degraded by grazing and logging activities in recent decades. Methods We conducted a factorial multi‐species experiment in which seeds and seedlings of five beneficiary species were sown in the presence and absence of three pioneer tree species. Beneficiary species performance was monitored for different ontogenetic stages. Results We found evidence of species‐specific facilitation in which the intensity and outcome of the interactions between nurse and beneficiary species varied depending on species identity. Additionally, for most combinations of nurse and beneficiary species, ontogenetic shifts from positive to neutral or negative interactions were observed with increasing beneficiary age. Conclusions We provide experimental evidence that nurse and beneficiary species identity simultaneously influence the balance between facilitation and competition. Our results suggest that ontogenetic shifts may be a widespread phenomenon in semi‐arid ecosystems. We discuss that a key mechanism explaining these findings is the match between what nurse species offer and what beneficiary species require in terms of resources and conditions. As a consequence, different nurse species tend to favour or inhibit unique sets of beneficiary species beneath their canopies. We argue that species‐specific facilitation is an overlooked mechanism promoting β‐diversity during community succession.

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Spondias tuberosa Arr., a fructiferous tree endemic to the northeast Brazilian tropical dry forest called Caatinga, accounts for numerous benefits for its ecosystem as well as for the dwellers of the Caatinga. The tree serves as feed for pollinators and dispersers as well as fodder for domestic ruminants, and is a source of additional income for local smallholders and their families. Despite its vantages, it is facing several man-made and natural threats, and it is suspected that S. tuberosa could become extinct. Literature review suggests that S. tuberosa suffers a reduced regeneration leading to population decrease. At this juncture S. tuberosa cannot be considered threatened according to the International Union for Conservation of Nature Red List Categories and Criteria, as it has not yet been assessed and hampered generative regeneration is not considered in the IUCN assessment. The combination of threats, however, may have already caused an extinction debt for S. tuberosa. Due to the observed decline in tree density, a thorough assessment of the S. tuberosa population is recommended, as well as a threat assessment throughout the entire Caatinga.Keywords: Spondias tuberosa, natural regeneration, conservation, IUCN red list, Caatinga.Spondias tuberosa Arruda (Anacardiaceae), uma árvore ameaçada de extinção da Caatinga?Resumo Spondias tuberosa Arr., é uma árvore frutífera endêmica da Caatinga, floresta seca tropical localizada no Nordeste do Brasil. A árvore traz diversos benefícios para o ecossistema e para a população local. Ela serve de alimento tanto para polinizadores e dispersores quanto para ruminantes domésticos e é fonte de renda extra para os agricultores familiares da região. Apesar de seus benefícios, esta árvore enfrenta várias ameaças naturais e antrópicas que podem levar a sua extinção. A revisão da literatura científica sugere que S. tuberosa sofre de reduzida capacidade de regeneração, o que leva à diminuição da população. Todavia, S. tuberosa não é considerada uma espécie ameaçada de extinção de acordo com as categorias e critérios da Lista Vermelha da União Internacional para a Conservação da Natureza, já que a espécie ainda não foi avaliada e capacidade regenerativa reduzida não é considerado critério pelo UICN. A combinação de ameaças, entretanto, pode já ter levado ao débito de extinção da S. tuberosa. Devido ao declínio observado da densidade das árvores, recomenda-se uma avaliação completa da população de S. tuberosa e uma avaliação de todas as ameaças sofridas pela árvore na Caatinga.Palavras-chave: Spondias tuberosa, regeneracao natural, conservação, lista vermelha da UICN, Caatinga.

Species of the subtribe Cassiinae present a wide diversity of floral types. Until recently it was considered that this diversity did not extend to their reproductive mechanisms. However, studies have recorded some variations in the enantiostylous pattern in this plant group. This study aims to investigate the morphological and functional variations of enantiostyly in species of the subtribe Cassiinae. Additionally, it proposes the recognition of enantiostylous types (ET) based on pollen deposition and capture mode. Morphological data were collected in fresh and fixed (alcohol 70%) buds and flowers, and also using photos and rehydrated material from herbarium sheets, for a total of 59 species. The parameters used to establish the ETs were pollination type, nature of pollen deposition on the pollinator body, deposition type, number of petals involved in pollen deposition, and pollen pathway. Morpho-functional features allowed the recognition of seven enantiostylous types (Flexuosa, Cana, Macranthera, Martiana, Amiciella, Repens and Ramosa) that present several levels of complexity. The type Ramosa was the most common and the Cana type was the least common. The types Repens, Martiana and Flexuosa do not have reciprocal pollen deposition, thus species with these types may be considered atypical. The groups resulting from similarity analysis partially coincide with the clades proposed in phylogenetic studies of Cassiinae. The recognition of functional ETs is important for understanding the evolution of reproductive strategies of Cassiinae species, and indicates an interesting line of investigation of enantiostyly in other plant groups.

In this paper we examine the number of known populations of 86 bromeliad species recorded in the Atlantic forest of north-east Brazil, to test the following predictions: (1) the current number of populations of most bromeliad species inhabiting the Atlantic forest of north-east Brazil is critically low, (2) the number of extant populations of a particular species is associated with the ecological attributes of the species, and (3) habitat loss determines, at least in part, the current distribution and number of populations of each species. At present there are at least 535 bromeliad populations in this forest but 61.6% of species have <6 populations and 24.4% have only one known population. The mean number of populations per species was significantly lower among species endemic to this part of the Atlantic forest, species recorded in only one vegetation type, forest and inselberg species, and obligatory epiphytic and terrestrial species. We were unable to relocate 41 populations recorded between 1920 and 1996, and populations of 20 species have become locally extinct. For these bromeliads geographic range, habitat specificity and life form appear to determine which species are more vulnerable to extinction. The species that have <6 extant populations include 27 species that are endemic to this forest. These species need to be evaluated for inclusion on both the IUCN and Brazilian Red Lists. Some of these species will only survive if the fragments containing the last populations are declared as protected areas.

ResumoNo Brasil, ocorrem 120 espécies do gênero Pseudobombax em diferentes formações vegetacionais. Espécies de Bombacoideae apresentam flores com antese noturna, visitadas por morcegos e esfingídeos. Objetivou-se investigar a biologia reprodutiva de P. marginatum, e conhecer relações entre planta e visitantes. O estudo foi desenvolvido em uma área de caatinga, no município de Afrânio, Pernambuco. Analisou-se a fenologia, biologia floral, comportamento dos visitantes e sistema reprodutivo. P. marginatum apresenta características de flores quiropterófilas, apesar de não receber visitas de morcegos, parecendo estar relacionado ao processo de fragmentação florestal ocorrente na área de estudo. A espécie floresceu entre maio e julho, recebendo visitas de esfingídeos, abelhas, vespas e aves. A produção de néctar foi elevada com baixa concentração de açúcares. Apenas na polinização cruzada obteve-se sucesso, devido à presença de mecanismos de incompatibilidade. P. marginatum apresenta-se em situação crítica quanto à sua regeneração, devido à carência de serviços de polinização eficientes, provavelmente ocasionados pela perturbação na área e ausência de quirópteros visitantes. Palavras-chave: fragmentação florestal, serviço de polinização, mecanismos de incompatibilidade. AbstractIn Brazil, the genus Pseudobombax is represented by some 120 species occurring in different vegetation types. Bombacoideae species have nocturnal flowers and are bat and hawkmoth visited. The aim of the work was to investigate the reproductive biology of P. marginatum, and to describe the plant-floral visitors relationships. The study was carried out in a Caatinga area in Afrânio municipality, Pernambuco state. Phenology, floral biology, flower-visitor behavior and reproductive system were analyzed. P. marginatum has chiropterophilous flowers, although it is not visited by bats, a fact possibly related to the forest fragmentation process in the study area. The flowering period of the species was from May to July, -floral visitors were hawkmoths, bees, wasps and birds. Nectar production was high with low sugar concentration. Reproductive success was obtained only in cross pollination, due to the incompatibility mechanism. P. marginatum presents a critical situation for regeneration due to the lack of efficient pollination services, caused probably by forest fragmentation in the study area and the lack of chiropterans visitors.

Monomorphic enantiostylous species produce flowers with a displacement of the style to the left (L) or right (R) on the same individual, and may exhibit different dynamics for the production of these floral types, which may influence levels of selfing. We investigated the production dynamics of L and R floral types in seven species and a variety of monomorphic enantiostylous species of the genera Senna and Chamaecrista. Our hypothesis was that most species present similar proportions of floral morphs each day. Individuals were classified daily over a period of 7 days according to the functional status, i.e. the proportion of floral morphs as functionally L, R or reciprocal (REC, i.e. similar proportions of the two floral morphs), and also according to the number of consecutive days in which they exhibited the same functional status. All species presented low daily flower production. Most species had individuals classified as functionally R, L and REC, and tend to repeat the same functional status over a few days, although they may change functional status during the flowering period. All species exhibited individuals that were classified as functionally reciprocal when both the daily and total number of flowers produced over 7 days was considered. The occurrence of different functional status has not yet been reported in the literature for enantiostylous species. The distinct strategies observed in the dynamics of floral morph production seemed likely to minimise geitonogamy and to favour cross-pollination between individuals (xenogamy).

A temperatura atua intimamente sobre a velocidade de absorção de água e igualmente sobre as reações bioquímicas que determinam tanto a velocidade e uniformidade de germinação. Por conseguinte, a viabilidade das sementes após períodos de armazenamento também pode ser um fator limitante no processo germinativo, minimizando o vigor. Diante disso, o presente trabalho teve como objetivo avaliar distintos períodos de armazenamento e temperaturas no comportamento germinativo de sementes de Schinopsis brasiliensis. O delineamento experimental adotado foi inteiramente casualizado, distribuídos em esquema fatorial 5x5, referentes a cinco tempos de armazenamento de sementes de S. brasiliensis armazenados em períodos distintos e cinco temperaturas constantes. Foram utilizados lotes de baraúna com período de armazenamento de 0, 12, 60, 72 e 84 meses, com quatro repetições. Calculou-se a percentagem de germinação, tempo médio de germinação, índice de velocidade de germinação, velocidade média de germinação e índice de Timson. Todos os parâmetros germinativos avaliados foram afetados significativamente. A viabilidade de sementes de S. brasiliensis é decrescida consideravelmente a partir de 12 meses de armazenamento. A temperatura e o tempo de armazenamento são fatores que influenciam diretamente o desenvolvimento inicial de sementes de S. brasiliensis. Palavras-chave: Anacardiaceae; germinação; espécies nativas; viabilidade; Caatinga.   STORAGE TEMPERATURE TIME IN GERMINAL BEHAVIOR Schinopsis brasiliensis ENGLER   ABSTRACT:  The temperature acts closely on the speed of water absorption and also on the biochemical reactions that determine both the speed and uniformity of germination. Therefore, the viability of the seeds after storage periods can also be a limiting factor in the germination process, minimizing vigour. Therefore, this study aimed to evaluate different storage periods and temperatures in the germination behavior of seeds of Schinopsis brasiliensis. The experimental design adopted was entirely randomized, distributed in a 5x5 factorial scheme, referring to five lots of S. brasiliensis seeds stored in different periods and five constant temperatures. Barauna batches with storage periods of 0, 12, 60, 72 and 84 months were used, with four repetitions. The germination percentage, mean germination time, germination speed index and Timson index were calculated. All germination parameters evaluated were significantly affected. The viability of S. brasiliensis seeds is considerably decreased from 12 months of storage. Temperature and storage time are factors that directly influence the initial development of S. brasiliensis seeds. Keywords: Anacardiaceae; germination; native species; viability; Caatinga.