Lack of Ecotypic Differentiation: Plant Response to Elevation,Population Origin,and Wind in the Luquillo Mountains,Puerto Rico1

How important is ecotypic differentiation along elevational gradients in the tropics? Reciprocal transplants of two shrubs, Clibadium erosum (Asteraceae) and Psychotria berteriana (Rubiaceae), and a palm, Preitoea acuminata var. montana (Palmaceae), were used to test for the effect of environment and population origin on growth and physiology in the Luquillo Experimental Forest of Puerto Rico. Two sites were used, one at Pico del Este (1000 m in cloud forest) and one at El Verde (350 m in lower montane rain forest). At the cloud forest site, plastic barriers were erected around a subset of the plants to examine if protection from wind affected survival or biomass accumulation. Survival of C. erosum and P. berteriana was not affected by site, population origin, or the presence of barriers. For P. acuminata var. montana, survival was higher for plants with barriers, but not affected by site and population origin. Plants of C. erosum and P. berteriana at El Verde grew larger than at Pico del Este, but there was no effect of population origin or barrier treatment on biomass accumulation for these species. For P. acuminata var. montana, there was no effect of environment, population origin, or barrier treatment on biomass accumulation. Light‐saturated photosynthetic rate (A_max) of C. erosum, P. berteriana, and P. acuminata var. montana, as well as leaf anatomical characteristics of C. erosum, were unaffected by environment, population origin, and barrier treatment. On balance, there seems to be little evidence of ecotypic differentiation in these species along the gradient.     

Effects of light,moisture, temperature,and litter on the regeneration of five tree species in the tropical montane wet forest of Puerto Rico

Field experiments were conducted to investigate the effects of light, moisture, temperature, and litter on the regeneration of two early-, one mid-, and two late-successional tropical tree species. High light and litter seem to be universally good cues for regeneration, increasing seed/seedling survival for all species except for Cecropia (an early-successional species) whose small seeds may not be able to penetrate the litter layer. In addition, the high temperature environment in both artificially shaded and nonshaded areas of a natural gap exhibits less seed loss, an increase in the percent and rate of germination, and an increase in seedling survival for Dacryodes (a late-successional species), than the lower temperature environment under an intact canopy. Low soil water is also a good cue for Dacryodes germination as it is for Prestoea and Cecropia. Finally, the lower temperature environment found under the forest canopy (compared to the natural gap) leads to less seed loss and more germination for Guarea (a mid-successional species). Our results suggest that a good patch for regeneration of many species in this forest, early- as well as late-successional species, would have high light and a litter layer that moderates temperature and moisture extremes. The substantial variation in suitability among regeneration filters and species could: (1) contribute to low establishment success, i.e., most dispersed propagules do not become trees, (2) make it difficult to group species into germination strategies, and (3) make it hard to generalize about a net effect of any specific environmental variable on establishment. We suggest that tropical disturbances should be viewed in terms of their impact on a variety of environmental cues, which may signal germination and impact subsequent growth and survival.     

中国繁缕属的一些分类问题

研究了36种中国产繁缕属(Stellaria)植物,根据模式材料或仅根据原描述,将已合格发表的1组、l系、12种、4变种和1变型首次归并到有关各类,依次列举人异名录中,其中有1移属。讨论了各种错误鉴定,同时对于选择性状、设想进化过程和分布记录均有讨论.     

五福花科花部维管结构的比较研究

首次报道了华福花属华福花 Sinadoxa corydalifolia和东方五福花 Adoxa orientalis花部维管结构,并对五福花科3属4种植物的花部维管系统进行了比较研究。3属4种的花部维管系统表现出不同的对称性和不同的复化、减化以及不同的融合程度。基于花部维管系统的证据,本工作支持四福花属四福花 Tetradoxa omeiensis为科内原始类群代表的看法。     

Patterns of litter production across a salinity gradient in a Pterocarpus officinalis tropical wetland

Historically, Pterocarpus officinalisJacq. (Leguminoseae) dominated freshwater wetlands in the coastal plains of Puerto Rico, but deforestation has reduced its distribution to small patches adjacent to mangrove forests in areas of higher salinity. The objective of this study was to determine how a gradient in soil salinity affected litter, flower, and fruit production in a Pterocarpus officinalis.Three 100 m² plots were established in each of three sites along a salinity gradient: pasture/Pterocarpus edge (low salinity, mean salinity at 60 cm–9.7 g Kg^–1), Pterocarpus forest (intermediate salinity, 11.5 g Kg^–1) and a Pterocarpus/mangrove ecotone (high salinity, 15.0 g Kg^–1). Across this gradient, P. officinalis accounted for 100% of the relative basal area in the low and intermediate sites and 43% in the high salinity site which was domimated by Laguncularia racemosa. The basal area of P. officinalis decreased along the gradient from 73.5 m² ha^–1 in the low salinity site to 42.0 m² ha^–1 in the high salinity site. Litterfall was sampled on average every 23 days in 45 0.25 m² traps (5 traps per plot) for two years. Annual litterfall for the forest was 11.9 Mg ha^–1 yr^–1. Peaks in litterfall were associated with high precipitation in May 1995 and tropical storms in September 1995. Leaf fall of P. officinalis was significantly higher in the low salinity site (4.8 Mg ha^–1 yr^–1) than the high salinity site (1.8 Mg ha^–1 yr^–1), but total stand litterfall was greatest in the area of high salinity due to the greater contribution of L. racemosa. Pterocarpus flower and fruit production was approximately 10 times greater in low and intermediate salinity sites in comparison with the high salinity site. An increase in global temperature, will lead to higher sea level and higher soil salinity in costal wetlands. To conserve this wetland forest type it is critical to expand the distribution into areas of lower salinity where this species occurred historically.     

Reproduction in an aggregating grouper,the red hind,epinephelus guttatus

Synopsis We examined the reproductive pattern of an aggregating grouper, the red hind,Epinephelus guttatus, in Puerto Rico. Macroscopic and histological examination of gonads confirmed that, although mature, ripe ovaries are found over a three-month period, spawning activity is limited to about 2 weeks each year. Females are determinate spawners and individuals are able to spawn more than once during the course of the annual spawning season. The red hind is protogynous and 50% maturity is attained at 215 mm fork length. In western Puerto Rico, spawning occurs in aggregations at several sites within loosely defined areas located towards the edge of the insular platform. Sex ratios of individuals taken by hook and line at one of the aggregation areas over a consecutive six-year period, suggest considerable intra- and inter-annual variation most likely attributable to a combination of differential ingress and egress by males and females during the course of an aggregation and to fluctuations in recruitment, differential mortality by sex and sex change among years. A comparative assessment of the reproductive patterns of seven western AtlanticEpinephelus spp. suggests that aggregation-spawning is associated with medium- to large-sized groupers, while smaller groupers do not aggregate. Mating systems vary among congeners in association with trends in male-female size dimorphism, sexual pattern and sperm competition. The short-term, localized, nature of spawning aggregations renders species with this reproductive mode particularly vulnerable to fishing pressure at spawning sites. Aggregating species, therefore, may require special management consideration.