Reproductive Phenological Patterns Research Articles

Impacts of inter-annual climate variability on reproductive phenology and postnatal development of morphological features of three sympatric bat species

Inter-annual variation in weather conditions has been shown to affect the reproductive phenological patterns of many organisms. Because of their relatively small body size and dependence on ectothermic prey, temperate-zone insectivorous bats are particularly sensitive to adverse spring environmental conditions that affect the duration of gestation and timing of parturition in these animals. This study aimed to compare phenological recruitment, birth seasonality and synchrony and morphological changes during postnatal growth in Rhinolophuseuryale, Rhinolophusferrumequinum and Myotisemarginatus in two consecutive years representing a typical dry (2015) and an extremely wet climatic event (2016) in a nursing colony in Kerend cave, western Iran. Females of these three bat species arrived from their wintering cave to the nursing colony in late April to mid-May each year. Synchrony of parturition as defined by amount clustering of births within a year assessed by circular statistics showed that for R. euryale and R. ferrumequinum the angular variance in dry year were significantly (P < 0.05) lower than in wet year, indicating a low level of synchrony in 2016. Similar comparison showed that births from M. emarginatus were highly synchrony, and there were no significant differences in timing of births among years (P > 0.05). Generalized estimating equation (GEE) for R. euryale indicated that for body mass and forearm length tests of parallelism (interaction term or growth rate) and tests for equal intercepts (y-intercepts or group term) were significant (P < 0.001). In R. ferrumequinum, the initial (y-intercepts) forearm length and body mass were not significantly (P > 0.05) different between the 2 years, but the tests for parallelism showed a significant decrease in growth rates of body mass and forearm length in the wet year (P < 0.05). Similar comparison in M. emarginatus indicated that for body mass, tests of parallelism were significantly different (P = 0.004), while tests for equal intercepts were not (P = 0.23). Our results suggest that climate changes may have unequal effects on different bat species due to differences in foraging habitat, niche partitioning, reproductive requirements and foraging strategies.

Temperature as the main factor affecting the reproductive phenology of the dioecious palm Mauritiella armata (Arecaceae)

Our research focused on the reproductive phenology of Mauritiella armata, a key veredas species in southeastern Brazil, and aspects of its floral and fruit morphology and sexual system. We observed the reproductive phenological patterns of M. armata for 36 months, and examined the relationships between phenophases and environmental variables to describe its phenological patterns in relation to environmental filters, as well as its floral and fruit morphologies, sexual system (to evaluate dioecy), and the biometry of its reproductive parts. Flowering was observed in the dry season and at the beginning of the rainy season, with fruiting occurring during the rainy season. The reproductive phenophases responded to environmental seasonality, principally temperature in the period immediately preceding the expression of the phenophase, as well as to environmental variations that had occurred up to six months earlier. The dioecious sexual system of M. armata was confirmed, with flowering synchronization between the sexes. The population studied did not exhibit apomixis, having xenogamy as its reproductive system. The staminate inflorescences were larger than the pistillate inflorescences and had greater numbers of flowers, although the pistillate flowers were larger. Wind pollen dispersal was not observed, thereby indicating that this species requires biotic pollination for fruit production.

Phenological patterns of Oreopanax fulvus (Araliaceae) in remnants of Araucaria Rainforest in Paraná, Brazil

Abstract Oreopanax fulvus is a species endemic to the Brazilian Atlantic Forest, assessed as rare and vulnerable in the states of Paraná and Rio Grande do Sul, respectively. This adverse situation requires conservation actions that must be supported by the understanding of its autecology. We aimed to identify the phenological patterns of O. fulvus populations from two Araucaria Rainforest remnants in Paraná. Monthly phenology monitoring of 19 trees in each site was performed over 24 months. We quantified the vegetative (i.e., leaf flushing, mature leaves, and leaf-senescence) and reproductive phenophases (i.e., buds production, blooming, immature, and mature fruits). Circular statistics based on activity index were applied to identify the phenophases seasonality. Spearman correlations were performed among phenophases and meteorological parameters. Leaf flushing and mature leaves were recorded in all months, with a decrease of mature leaves during November and December. Leaf-senescence was seasonal, occurring from May to December. The reproductive phenophases were seasonal: blooming from January to May; and fruiting from March to November, with fruits starting to mature in September. Vegetative and reproductive phenophases were highly influenced by average temperature and photoperiod. Although there were dissimilarities in reproductive phenological patterns, the different populations studied had similar phenological performances.

PHENOLOGY OF Copernicia alba IN FLOODED AND NOT FLOODED ENVIRONMENTS

The objective of this study is to describe the reproductive and vegetative phenological patterns of individuals of Copernicia alba, popularly known as "carandá", present in a flooded and non-flooded environment and to test the relations between vegetative and reproductive phenophasesand climatic seasonality. The phenological aspects of the carandá were obtained through a biweekly observation of 22 individuals from two areas of the Pantanal of Mato Grosso between August 2015 and August 2017. The carandá population presented a perennial behavior, flowering during the dry season and a greater leaf intensity in the transition period to the rainy season. Budding, although continuous, was intense in the rainy season, and the leaf deciduous pattern had a direct interference from the absence of rainfalls in the dry period. The incidence of floral buds occurred in the dry period, and the flowering occurred between the dry and rainy periods. The fruiting period occurred in the rainy season, indicating a high synchronism of phenophases.

FENOLOGIA REPRODUTIVA DE RUBIACEAE JUSS. NA MATA ATLÂNTICA PARAIBANA

Phenological studies help determine the reproductive and vegetative patterns of plants, contributing to knowledge about dynamics in an environment. We studied the reproductive phenological patterns of five Rubiaceae species in an Atlantic Forest area, evaluating their seed dispersal syndromes and the effects of climatic variables on flowering and fruiting phenology. We monitored reproductive individuals of five species biweekly from February 2015 to February 2016 (one-year period). For each reproductive phenophase, we evaluated the Fournier index and intrapopulational synchronicity. Spearman’s rank correlation was used to determine possible correlations between phenological phenophases and rainfall, temperature and photoperiod. Seed dispersal syndromes were based on morphological analysis and Van der Pijl classification. The Rubiaceae community showed a continuous pattern of flowering and fruiting. However, when analysing phenological patterns by species, there was a higher concentration of phenophases and synchronicity of populations in the rainy season. Flowering and fruiting were positively correlated with temperature and historical average rainfall. Zoochory was the predominant seed dispersal syndrome, indicating the importance of the Rubiaceae family as a year-round resource for frugivorous communities. Temperature and rainfall regulate the reproductive phenophases similarly, resulting in a high level of synchrony between them.

Phenology of Copernicia alba in Flooded and Not Flooded Environments

The objective of this study is to describe the reproductive and vegetative phenological patterns of individuals of Copernicia alba , popularly known as caranda, present in a flooded and non-flooded environment and to test the relations between vegetative and reproductive phenophasesand climatic seasonality. The phenological aspects of the caranda were obtained through a biweekly observation of 22 individuals from two areas of the Pantanal of Mato Grosso between August 2015 and August 2017. The caranda population presented a perennial behavior, flowering during the dry season and a greater leaf intensity in the transition period to the rainy season. Budding, although continuous, was intense in the rainy season, and the leaf deciduous pattern had a direct interference from the absence of rainfalls in the dry period. The incidence of floral buds occurred in the dry period, and the flowering occurred between the dry and rainy periods. The fruiting period occurred in the rainy season, indicating a high synchronism of phenophases.

Pollination, Mating System, Phenology and Characterisation of Medinilla multiflora Merr. (Melastomataceae) on Mt Makiling, Philippines

An investigation into the reproductive biology of Medinilla multiflora Merr. (Melastomataceae) from Mt Makiling, Luzon, is presented. This includes a morphological and distributional examination of the population on the mountain, the documentation of reproductive phenological patterns, a study of the mating system and observations of biotic interactions. Measurements were made of trait variability, reproductive phenology was characterised from field and herbarium observations, stigmatic receptivity was tested by counting pollen germination, insect exclusion and hand-pollination experiments helped determine the mating system and field observations recorded the identity and behaviour of floral visitors. Significant reproductive morphological differences were found between described populations. This identified a need for the recognition of this diversity and further delimitation of the Medinilla multiflora species complex. Although Medinilla multiflora produced flowers and fruit year-round, the population also exhibited cycles of increased reproduction most likely initiated by seasonal low temperatures. Medinilla multiflora was found to require pollination but not cross-pollination. Two major peaks in stigmatic receptivity occurred throughout the day and the majority of pollen was found to be viable. Generalist bees proved to be the primary pollinators of the study population and were most active in the morning depending on weather conditions. Generalist pollinators and self-compatibility are advantageous traits for establishment and persistence in isolated mountain habitats; however, losses of this habitat due to climate change could have profound consequences for the future success of Medinilla multiflora.

Phenodynamics of five orchids species growing on rock outcrops in the Chapada Diamantina Mountains in northeastern Brazil

We evaluated the vegetative and reproductive phenological patterns of the orchids Cattleya elongata, Cyrtopodium aliciae, Epidendrum orchidiflorum, Epistephium lucidum, and Sobralia liliastrum (Orchidaceae) growing on sandstone outcrops in the Chapada Diamantina Mountains in northeastern Brazil. Phenological events were associated with abiotic factors, leaf longevity, life form, plant growth pattern, and pollination syndrome. Phenological observations were made for 18 months and followed the phenophases of: stem/pseudobulb emission, leaf flush, leaf fall, flowering, immature fruit and mature fruit. Seasonality, synchrony, and correlations between phenophases and environmental variables were tested. The orchid species demonstrated aseasonal vegetative phenologies, except for pseudobulb emission. Reproductive events were seasonal, except for flowering in E. orchidiflorum. There was high flowering overlap between the species pairs S. liliastrum and C. aliciae (dry season) and C. elongata and E. lucidum (rainy season). Dispersal occurred during both the rainy and dry seasons. The vegetative phenophases exhibited low synchrony, and were related to certain morphofunctional characters (stems/pseudobulbs, CAM metabolism). The reproductive phenophases showed high synchrony consistent with the deceit pollination strategy usually associated with the group.

Is the phenology of all restinga species the same? A taxonomically-focused study of Sapindaceae in a highly threatened coastal environment

Restingas are highly threatened coastal ecosystems located in the Atlantic Forest domain that host a great diversity of plants, including many endemics. Though expanding transportation infrastructure and real estate development have rapidly destroyed extensive portions of natural restinga landscapes along the entire Brazilian coast, comparative phenological studies and conservation programs focused on protecting restinga species are extremely rare. As a result, we currently have a poor understanding of phenological patterns of most plant groups in this habitat. Therefore, aiming to answer the question “Is the phenology of all restinga species the same?”, we designed a taxonomically-focused comparative study of Sapindaceae in the Restinga da Marambaia, Rio de Janeiro, Brazil. The vegetative and reproductive phenology of four species with a diversity of life forms was analyzed over 24 months: Allophylus puberulus (shrub), Matayba intermedia (tree), Cupania emarginata (tree) and Paullinia coriacea (liana). We found that leaf flush and leaf fall occurred throughout the year for all species. However, they exhibited very different reproductive phenological patterns. Allophylus puberulus showed a nearly continuous, but irregular expression of reproductive phenophases throughout the year, while the other three species have distinct non-overlapping phenological maxima. We also investigated the relationship between phenology and environmental parameters. Most correlations were found with temperature and day length rather than precipitation. However, there was no strong, consistent pattern of phenological events correlating with abiotic stimuli. A detailed discussion of how these patterns compare with other phenological studies of Sapindaceae is included. We conclude that taxonomically focused phenological analyses provide a powerful perspective, and future studies coupling phenology with phylogenetics will yield further insight.

Vegetative and reproductive phenological patterns in coastal dunes in S Spain

The phenology of Mediterranean plant species has been extensively studied in different types of ecosystems. However, very little research has been conducted on dune ecosystems. The aim of this research is the phenological characterization and comparison among phenological patterns in three coastal dunes areas in S Spain. For this purpose, we apply the methodology proposed by Orshan (1989) and NLPCA phenological indexes. Our results show that seasonality of species from coastal dunes in S Spain follows the pattern observed in dry and warm Mediterranean ecosystems. The maximum phenological activity occurs for a period of 7-9 months, mainly in spring and late winter, whereas summer is clearly the most inactive period of the year. Vegetative phenophases predominate over the reproductive. Flowering is mainly early (March-May), but it may extend to summer. Flowering duration has been identified as a key index in the differentiation among coastal dunes with different conditions of Mediterranean macroclimate, whereas the importance of the phenophase sequence index has been shown in order to discriminate sectors within dunes. Using the NLPCA analysis based on phenological indexes, four phenological groups of species have been determined. From a conservation perspective, the identification of these groups point out the utility of developing different strategies of management according to the high diversity of eco- and phenomorphological variability that characterize the coastal dunes.

Fenologia reprodutiva e vegetativa de arbustos endêmicos de campo rupestre na Serra do Cipó, Sudeste do Brasil

Os Campos rupestres têm destaque no cenário mundial da conservação por sua enorme riqueza em espécies e alta taxa de endemismo. É considerado um ecossistema ameaçado devido à intensa e progressiva descaracterização que vêm sofrendo pela ação antrópica. O objetivo deste estudo foi descrever os padrões fenológicos reprodutivos e vegetativos em seis espécies arbustivas endêmicas dos campos rupestres da Cadeia do Espinhaço, simpátricas na Serra do Cipó, Minas Gerais, e testar a relação entre suas fenofases e a estacionalidade climática. Esperamos que as espécies tenham suas fenofases fortemente relacionadas às variações entre as estações seca e úmida. As observações fenológicas foram conduzidas mensalmente nas fenofases reprodutivas (flor, fruto e dispersão) e vegetativas (queda de folhas e brotamento). De acordo com a combinação dos padrões fenológicos reprodutivos, vegetativos e sazonalidade, foi possivel distinguir quatro estratégias fenológicas para as seis espécies avaliadas. Dessa forma, o presente estudo mostrou uma grande diversidade de padrões fenológicos, mesmo considerando o pequeno número de espécies amostradas. Por outro lado, em todas as espécies as fenofases reprodutivas apresentaram um padrão significativamente sazonal, com alta concentração de espécies reproduzindo em uma dada estação do ano, sugerindo uma importância destacada da sazonalidade do clima na definição dos padrões fenológicos em campos rupestres.

Reproductive phenology of bryophytes in tropical rain forests: the sexes never sleep

Events of the sexual reproductive cycle of 11 bryophyte species (mosses and liverworts with monoicous and dioicous sexual conditions) were described for two different sites (montane and sea level) of a Brazilian tropical rain forest, during a 15 month-period. The sex expression of many species was continuous over the whole period, irrespective of the seasons and the forest sites. The specific sexual conditions of dioicous species did not change, but synoicous species had strategies to increase the chances of out-crossing, bearing unisexual branches in addition to bisexual ones. The pattern of gametangia and sporophyte development was different among the species, but the same between the sites. There was a seasonal effect on the maturation of gametangia and sporophytes. Male gametangia were mostly mature by the end of the dry season. Fertilization occurred during the wettest months and sporophytes developed during the dry season, dispersal of spores mostly towards the end of the dry season. Female gametangia were receptive over the whole period, with many mature gametangia before the start of the rainy season. Male gametangia, in contrast to female, took longer to develop and aborted in high numbers. Bryophytes in tropical rain forests are favored by wet weather and mild temperatures. Similar reproductive phenological patterns were found in different habitats with minor variations.

Fenologia reprodutiva de Dipteryx odorata (Aubl.) Willd (Fabaceae) em duas áreas de floresta na Amazônia Central

Estudos fenológicos de longa duração em florestas tropicais são raros. Foi realizado o acompanhamento fenológico de Dipteryx odorata, no período de 1974 à 2000, em duas áreas de floresta amazônica: a Reserva Florestal Ducke (RFD) e Estação Experimental de Silvicultura Tropical (EEST). O objetivo foi observar os padrões fenológicos nas duas áreas, verificar a regularidade da floração e frutificação num período de 27 anos e a influência dos fatores climáticos nestes eventos. Foram marcados cinco indivíduos na RFD e cinco na EEST e observados quanto à produção de flores, frutos imaturos e maduros. A floração e a produção de frutos imaturos apresentaram padrão irregular nas duas áreas observadas, variando quanto a época de ocorrência e a duração entre anos e estações, mas apresentaram freqüência de ocorrência similar nos 27 anos observados. Para a fenofase frutos maduros este padrão foi diferente, com intervalos de até três anos sem ocorrência de frutos maduros, na RFD e de sete anos na EEST. Conclui-se que a freqüência de ocorrência das fenofases de floração e frutos imaturos foi anual e a de frutos maduros supra-anual, todas com padrão irregular e duração de intermediária a prolongada. Ocorreu variação de um a três anos entre episódios de floração e frutos imaturos e de um a sete anos entre episódios de frutos maduros, não ficando evidente, nesta análise, a influência dos fatores climáticos nos padrões observados. Sugere-se o uso racional dos produtos derivados de Dipteryx odorata, o cumaru, especialmente quanto à exploração de seus frutos e o desenvolvimento de mais estudos de longa duração, fundamentais para entender os padrões fenológicos reprodutivos e de oferta de recursos em florestas tropicais.

Estrutura populacional de Xylopia aromatica (Lam.) Mart. e de Roupala montana Aubl. em fragmentos de cerrado no Estado de São Paulo

In order to understand whether and how population structure of different species varies among different fragments and within the same fragment, we studied the ontogenetic stage and size distributions of two common cerrado tree species, in four cerrado fragments with different physiognomies and in three sites with similar physiognomies within the same fragment in the Municipality of Itirapina (22°15' S, 47°48' W), Sao Paulo state, SE Brazil. We recorded the height and the stem basal diameter (DSH) of all individuals with DSH > 3 cm in the six samples of 200 contiguous 5 x 5 m plots. Individuals with DSH < 3cm were sampled in 1 m² sub-plots at one corner of the plots. Xylopia aromatica had greater proportions of initial ontogenetic stages in open physiognomies, whereas Roupala montana had high proportion of initial stages and greater young:adult ratio in the densest physiognomy. The ontogenetic stage structure had greater differences among samples within the same fragment than among fragments, i.e., it varied in small spatial scales. The spatial heterogeneity of environmental factors (differences in vegetation cover that varied from open to dense), different reproductive characteristics (R. montana can reproduce asexually, whereas X. aromatica reproduces only by seeds) and phenological patterns (annual in X. aromatica, and supra-annual in R. montana) could be the main variables associated to the ontogenetic structure variation, and they would act differently upon each species in each site. Thus, each site of cerrado constitutes a different environment, which can differently influence the success of a species.

Phenology of woody species in tropical coastal vegetation, northeastern Brazil

The study was carried out in the Private Nature Reservation Nossa Senhora do Outeiro de Maracaípe, located along the southern coast of Pernambuco state, in the Nossa Senhora do Ó District (08°31′48″S and 35°01′05″W), Ipojuca municipality, northeastern Brazil. The reserve has 76.20 ha of tropical coastal vegetation ( Restinga forest). The aims were to determine the existence of seasonal phenological pattern of woody species as a function of rainfall. During the study period, the rainfall was 26.8 mm in the driest month (November 2003) and 538.9 in the wettest (June 2004). Observations on flowering, fruiting, leaf fall, and leaf flushing were recorded monthly, during 16 months (April 2003 to July 2004). All species with a ground level perimeter >10 cm and represented by at least three individuals, were selected and tagged. A total of 51 species represented by 156 individuals were recorded. Leaf flushing and leaf fall did not have seasonal variation and the species continued to gain and loose leaves during the dry (August to February) and rainy (March to July) seasons. Flowering, when evaluated by the Fournier's percentage, varied between 1.9% and 20.2%, with maximum intensity in December 2003 (16.4%) and January 2004 (20.2%). Likewise, fruiting varied between 3.8% and 21.4% with the highest percentages in February (17.2%) and March (21.4%) 2004. The analysis comparing reproductive phenological patterns with monthly rainfall did not show a significant correlation, which may suggest investigations concerning other factors, including biotic ones, as pollination and/or dispersal modes, which can be influencing reproductive events of plants in the studied Restinga forest.

Flora e aspectos auto-ecológicos de um encrave de cerrado na chapada do Araripe, Nordeste do Brasil

Este trabalho visa conhecer a composição e riqueza florística, os padrões fenológicos reprodutivos, as síndromes de dispersão e as formas de vida das espécies de uma disjunção de cerrado em clima semi-árido, na chapada do Araripe, Estado do Ceará. Foram encontradas 107 espécies e 41 famílias. Fabaceae, Myrtaceae, Poaceae, Apocynaceae, Euphorbiaceae e Malpighiaceae foram as mais ricas em espécies. Foi feita a distribuição geográfica de 47 espécies arbustivas e arbóreas em 27 listagens de cerrados brasileiros. Doze espécies apresentaram ampla distribuição geográfica e 13 foram registradas apenas neste trabalho. Cerca de 76% das espécies floresceram e frutificaram no período chuvoso. As síndromes de dispersão predominantes foram: zoocoria, autocoria e anemocoria. O espectro biológico foi predominantemente constituído por fanerófitos (50,7%), hemicriptófitos (14,9%) e caméfitos (13,1%). O cerrado estudado apresentou menor riqueza taxonômica que os cerrados contínuos e comportamento das fenofases reprodutivas, percentagem de síndromes de dispersão e formas de vida similares.

Reproductive phenology of the cerrado plant community in Emas National Park (central Brazil)

The cerrado, a savanna-like formation, is the second-most widespread vegetation type in Brazil. Its core region occupies the Brazilian Central Plateau, with a seasonal climate, including wet summer and dry winter. We studied the reproductive phenological patterns of the cerrado plant community in Emas National Park (central Brazil). Monthly field trips revealed 601 species, classified, according to their dispersal syndromes, into anemo-, auto-, or zoochorous species, when they were dispersed by wind, explosion or gravity, or animals, respectively. We analysed the flowering and fruiting patterns of the community in relation to dispersal syndromes, comparing the herbaceous and the woody components. The herbaceous component was characterised by a majority of autochorous species, and the woody component, by a majority of zoochorous species. There was a striking seasonality in the community-wide pattern of flowering and fruiting, although this was different between the herbaceous and the woody components. Woody species flowered mainly during late dry and early wet seasons, whereas herbaceous species flowered especially during late wet season. In the dry season, when their diaspores can be dispersed more efficiently, the proportions of anemo- and autochorous fruiting species were higher. During the rainy season, when their fruits can be kept attractive for longer time, the number of fruiting zoochorous species reached its peak.

Fenologia de Rubiaceae do sub-bosque em floresta Atlântica no sudeste do Brasil

Phenological studies of different species within a single family occuring in the same habitat, may help to understand the possible factors regulating the phenophases. During 14 months, we observed the vegetative and reproductive phenological patterns of ten understorey species of Rubiaceae of a Brazilian Atlantic forest, Nucleo Picinguaba, Sao Paulo State, Brazil. Leaf production and leaf fall occurred simultaneously in all studied species, throughout the observation period, resulting an evergreen appearance to the understorey. Flowering was also observed along the year, althougth the number of species flowering was higher during the wettest and hotest season. Our result contrasts with the seasonal flowering pattern observed for canopy species of Rubiaceae at the same area. The correlations between rainfall, temperature and Rubiaceae flowering were not significant. The fruit production was distributed along the study period, increasing at the end of the rainy season, resulting in a continuous availability of resources for frugivores. Reproductive phenological patterns differed among the Rubiaceae species in such a way that different factors seem to be regulating the phenophases of each species.

Vegetative and Reproductive Phenologies of a Palm Assemblage in Panama

During a 4-yr phenological study of the palm flora of Barro Colorado Island, Panama, palm species displayed substantial variation in reproductive phenology despite a shared uniform growth architecture. Reproduction in the majority of species was distinctly seasonal: most, but not all, initiated flowering sometime during the rainy season. In two species, individuals exhibited multiple flowering episodes. Palm species differed in the degree of within-year flowering synchrony but were relatively predictable in flowering time from year to year. Especially within asynchronously flowering species, fruiting was more synchronous than flowering, in part as a result of the failure of individuals flowering at certain times to produce mature fruit. Levels of flowering within each species were generally high except in the clonal Bactris palms, and it appeared for some species that canopy openness may stimulate flowering. Palm vegetative phenology was also seasonal and appeared more responsive to annual climatic variation than did reproductive phenology. In many species, rates of leaf expansion slowed during the dry season, an effect that was exaggerated during the prolonged El Ninio dry season of 1982-1983; however, a species' total annual leaf production was relatively constant from year to year. Leaf production correlated with individual height in some species, but was generally not related to the degree of canopy openness. The underlying significance of the variation in reproductive phenology within this palm flora remains largely unexplored. MANY TROPICAL PLANT COMMUNITIES display conspicuous seasonal patterning in vegetative and reproductive phenologies at both community and species levels (Fournier & Salas 1966, Medway 1972, Frankie et al. 1974, Monasterio & Sarmiento 1976, Foster 1982), despite the apparent absence of the very dramatic photoperiodic and climatic fluctuations that regulate temperate zone plant phenologies. Although alternative mechanisms such as rainfall patterns have been suggested as the phenological signals for tropical species (e.g., Opler et al. 1976, Augspurger 1982), the resulting phenological patterns are presumed to represent adaptive responses, whatever the proximate cues may be. Adaptive strategies for successful pollination and seed dispersal are frequently invoked to explain plant reproductive timing (e.g., Janzen 1967, Stiles 1978, Augspurger 1981); however, Borchert (1983) has cautioned that constraints of physiology and vegetative morphology must be considered before interpreting reproductive phenologies from the standpoint of biotic interactions with pollinators and seed dispersers. One group of tropical plants, the palms, offers an opportunity to evaluate morphological constraints on reproductive phenology because their growth pattern is essentially uniform. The monopodial palm stem grows continuously from a single meristem and produces new leaves sequentially, with a corresponding sequential death and shedding of old leaves (Corner 1966). A single axillary inflorescence bud can be initiated at each leaf node at the time of leaf formation, and flowering commences upon the rapid enlargement and expansion of these preformed buds. This shared growth pattern may limit the range of possible reproductive phenological patterns among palm species, and a continuous leafing phenology would provide the potential for aseasonal reproductive activity throughout the year because of the direct association between inflorescence buds and developing leaves. We examined these potential restrictions upon reproductive phenology in a 4-yr study of the palm flora of a tropical lowland forest on Barro Colorado Island, Panama. Here we address three questions about palm phenologies: (1) is vegetative growth seasonal or aseasonal; (2) is reproduction correspondingly seasonal or aseasonal; and (3) does reproductive phenology vary among species, or is it relatively consistent from the phylogenetic constraints imposed by similar growth morphology. In considering the phenologies of members of a defined taxonomic group within a community, we focus our study at an intermediate level between whole-community surveys (e.g., Frankie et al. 1974) and studies of single species (e.g., Augspurger 1981). Our analysis is performed at the levels of the individual plant and plant population; inflorescence phenology as it relates to breeding systems (e.g., Bullock 1981, Beach 1984) is not considered here. We utilize quantitative data from sample populations of each species to measure relative synchrony and seasonal constancy in phenological timing and to assess the reproductive performance of these species populations. I Received 2 November 1985, revision accepted 9 April 1986. 2 Present address: Department of Biological Sciences, University of Wisconsin, Milwaukee, Wisconsin 53201, U.S.A. 3Present address: Department of Botany, University of Florida, Gainesville, Florida 32611, U.S.A. 342 BIOTROPICA 19(4): 342-356 1987 This content downloaded from 157.55.39.132 on Thu, 15 Sep 2016 04:54:48 UTC All use subject to http://about.jstor.org/terms