Salvador Montiel

Bat assemblages in a naturally fragmented ecosystem in the Yucatan Peninsula, Mexico: species richness, diversity and spatio-temporal dynamics

Investigations of bats in naturally fragmented ecosystems may help refine assumptions about bat responses to fragmentation of their habitats by human activity. Bat species assemblages were studied for a 3.5-y period in a naturally fragmented landscape in the north-west Yucatan Peninsula, Mexico. Bats were systematically sampled using mist nets in a total of 16 forest islands of four categories (four sites each): large (> 20 ha), small ( 10 km or < 1 km away from the nearest forest island, respectively). We captured a total of 1134 bats representing 17 species. Bat diversity and species richness were similar among categories of forest island. Fruit-eating bats (78-93% of captures) were significantly more abundant in large and in small than in forest islands in the far or near categories. Differences in density of Manilkara zapota trees in the forest islands might underlie the observed variations in the abundance of frugivorous bats. Distances traversed by bats (0.65-38 km) between forest islands (typically 100-300 m away), facilitates the mobility of bats across the landscape. However, the moderately rich bat species assemblage detected, suggests that other species may not be able to persist in such naturally fragmented ecosystems.

Seed bank dynamics of the desert cactus Opuntia rastrera in two habitats from the Chihuahuan Desert

In desert environments the main input to the seed bank of many succulents is the seed rain through zoochory while high levels of granivory by rodents, birds and ants are the main cause of subsequent losses. In the patchy environment of arid lands the characteristics of both processes may vary between habitats causing differences in the recruitment of new genets. To test this hypothesis we used populations of the desert cactus Opuntia rastrera which has different recruitment rates in the two adjacent habitats where it grows. In Opuntia-dominated scrublands (nopaleras, density ca. 4,000 plants/ha) 1 seedling out of 7,000,000 seeds establish, whereas in grasslands (density ca. 100 plants/ha) this ratio is 1:20,000. From 1996 until 1998 the seed rain, seed removal by granivores and seed abundance in the soil were monitored in both habitats. Results showed striking differences in the dynamics of the seed bank of both habitats. Seed rain was 8.5 times bigger in nopaleras than in grasslands. In nopaleras most seeds were removed by rodents while the quantities of seeds removed by rodents, birds and ants in grasslands were similar. One year after dispersal (the time necessary to break seed dormancy) only 6% of original nopalera seeds and 12% of grassland seeds remained. After germination trials only 1% (ca. 15,000 seeds/ha) and 2% (ca. 2,500 seeds/ha) respectively were viable. These differences in the effective seed bank (6 times bigger in nopaleras) can not explain the differences in genet recruitment (which is several orders of magnitude bigger in grasslands). Apparently the between habitat difference in nurse plant availability and in rodent density (which inflict a strong hervibory upon seedlings) can explain the differences in genet recruitment. It is speculated that this between habitat difference in genet recruitment suggests that the species evolved in less extreme environments (e.g. grasslands) than desert scrublands which, in turn, are colonised due to the singular ability of O. rastrera for vegetative propagation.

Patch size and isolation predict plant species density in a naturally fragmented forest.

Studies of the effects of patch size and isolation on plant species density have yielded contrasting results. However, much of the available evidence comes from relatively recent anthropogenic forest fragments which have not reached equilibrium between extinction and immigration. This is a critical issue because the theory clearly states that only when equilibrium has been reached can the number of species be accurately predicted by habitat size and isolation. Therefore, species density could be better predicted by patch size and isolation in an ecosystem that has been fragmented for a very long time. We tested whether patch area, isolation and other spatial variables explain variation among forest patches in plant species density in an ecosystem where the forest has been naturally fragmented for long periods of time on a geological scale. Our main predictions were that plant species density will be positively correlated with patch size, and negatively correlated with isolation (distance to the nearest patch, connectivity, and distance to the continuous forest). We surveyed the vascular flora (except lianas and epiphytes) of 19 forest patches using five belt transects (50×4 m each) per patch (area sampled per patch = 0.1 ha). As predicted, plant species density was positively associated (logarithmically) with patch size and negatively associated (linearly) with patch isolation (distance to the nearest patch). Other spatial variables such as patch elevation and perimeter, did not explain among-patch variability in plant species density. The power of patch area and isolation as predictors of plant species density was moderate (together they explain 43% of the variation), however, a larger sample size may improve the explanatory power of these variables. Patch size and isolation may be suitable predictors of long-term plant species density in terrestrial ecosystems that are naturally and anthropogenically fragmented.

Continuous forest has greater taxonomic, functional and phylogenetic plant diversity than an adjacent naturally fragmented forest

Several studies have evaluated the short-term effects of tropical forest fragmentation on plant taxonomic diversity, while only a few have evaluated its effects on functional or phylogenetic diversity. To our knowledge no study has looked at the long-term consequences of tropical forest fragmentation on the three main components of plant diversity simultaneously: taxonomic, functional and phylogenetic diversity. We sampled the vascular flora using belt transects (50 × 4 m) in a continuous tropical semi-evergreen forest (16 transects) and in an adjacent naturally fragmented forest (fragments of 1.7-My-old semi-evergreen forest immersed in a mangrove/sedge matrix) (18 transects), and compared their taxonomic, functional and phylogenetic plant diversity. There were 36 species in the continuous forest and 28 in the fragmented forest. Continuous forest was taxonomically more diverse (25%) than thefragmentedforest.All functionaldiversitymetrics were greater (6-33%)inthecontinuous thaninthe fragmented forest. Phylogenetic diversity was 19% greater and phylogenetically more overdispersed in the continuous forest than in the fragmented forest. The results suggest that in the fragmented forest not only is taxonomic plant diversity lower, but functional and phylogenetic diversity are as well. The negative effects of forest fragmentation on plant diversity seem to be chronic.

The Practice and Perception of Batida (Group Hunting) In A Maya Community of Yucatan, Mexico

Abstract The batida, or traditional group hunting, practiced by the Maya of the Yucatan Peninsula provides hunters with wild meat to sustain their families. Our study of batida hunting trips in the Los Petenes community during a 6-month period (2008–2009) provided information on the participants, the practices, and the results. Maya peasant-hunters targeted deer (Odocoileus virginianus, 81%) and peccary (Pecari tajacu, 19%), obtaining on average 2.3 kg of meat per participant. In Los Petenes the batida is open to all adult men who wish to participate within its merit-based hierarchical structure, organized by two hunters recognized for their outstanding abilities. Interview data indicates that in addition to meat, the batida provides its participants with a reinforcement of their cultural identity as Maya peasant-hunters, a sense of belonging to the group and the community, and the chance to gain prestige as hunters. We argue that these social dimensions of the batida, complemented by the practical goal of meat provision, maintain this practice in the community, and very possibly in other communities of Maya heritage.

Reproductive Seasonality of Fruit-Eating Bats in Northwestern Yucatan, Mexico

In the tropics, rainfall seasonality seems to be the most important factor affecting bat reproductive cycles, triggering reproductive activity or by its indirect affect on the availability of food resources. Considering this, we studied the reproductive phenology of three phyllostomid fruit-eating bats (Artibeus jamaicensis, Dermanura phaeotis and A. intermedius) in a markedly seasonal coastal wetland in northwestern Yucatan Peninsula. Bats were sampled with mist nets during a consecutive 3-year period in 16 naturally formed forest islands and we assessed the reproductive condition of captured bats during the dry and rainy seasons. Sampling effort of 196 nights (11,100 net-hours), resulted in the capture of 738 individuals of A. jamaicensis (40%), D. phaeotis (32%), and A. intermedius (28%). At least 91% of the males captured showed reproductive evidence (males with testes descended) for the three species throughout the year. For D. phaeotis and A. intermedius we detected seasonal changes in reproductive activity of females associated with rainfall seasonality. In these two bat species a higher abundance of pregnant females during the dry season and presence of lactating females in both seasons indicated a seasonal polyoestry pattern (with an emphasis of pregnancy and births in the dry and early rainy season, respectively). In the case of A. jamaicensis, a similar abundance of reproductive females (pregnant or lactating) between seasons suggested the existence of an aseasonal polyoestry pattern for this species. Fruit availability in the study area might influence the reproductive patterns observed for the three bat species.

Local perceptions of wildlife use in Los Petenes Biosphere Reserve, Mexico: Maya subsistence hunting in a conservation conflict context

Conservation conflicts can arise in biosphere reserves when local people face restrictions on resource use and access, mainly in terms of subsistence. We studied the potential conservation conflict with subsistence hunting in two Maya communities (Los Petenes and El Remate) located in the zone of influence of Los Petenes Biosphere Reserve, Mexico. Perceptions, interests and expectations of stakeholders regarding subsistence hunting in the reserve were recorded through semi-structured and in-depth interviews of peasant-hunters and reserve authorities, and participant observation was carried out in both communities. A total of 66 peasant-hunters were identified in Los Petenes (62%) and El Remate (38%). Overall, peasant-hunters acknowledged hunting for family subsistence and expressed the conviction to continue hunting in the region. They mentioned their enthusiasm for hunting, mainly individually and aimed at obtaining white-tailed deer (Odocoileus virginianus) and perceived a recent reduction in potential prey locally. Although the law in Mexico does not prohibit subsistence hunting, external authorities stated that they have announced a generalized ban on hunting based on the precautionary principle to simplify enforcement both inside and outside the reserve. The de facto restriction on wildlife use, even for subsistence purposes, which was mentioned by external actors, conflicted with the local need and expectation of the contemporary Maya hunters to continue subsistence hunting in the region. Our study confirms the existence of a conservation conflict associated with this traditional practice in the reserve and provides necessary information for managing such conflict.

Stakeholder Linkage in Conservation Strategies: A Qualitative Tool for Improving the Management of a Biosphere Reserve in the Yucatan Peninsula, Mexico

Management strategies for biosphere reserves need to be locally linked, acknowledging the interests and expectations of local stakeholders, as their participation is crucial for effective resource conservation, particularly in the case of subsistence resource management. In this paper we present a novel qualitative analysis tool, called a linkage matrix, for evaluating the social linkage of biosphere reserve management instruments. As a case study we considered wildlife use for subsistence purposes in the context of Los Petenes Biosphere Reserve (LPBR), located in the northwest of the Yucatan Peninsula, Mexico. Based on official and ethnographic data on traditional wildlife use in two Maya communities neighboring the reserve, we documented its Management Programs degree of social linkage, and identified actions to improve its implementation in the zone of influence of the protected area. Based on the linkage matrix, the reserve Management Program was found to be highly inclusive, taking into account 64% of the interests and expectations identified by local peasant-hunters regarding wildlife. Nevertheless, marked deficiencies were identified in the implementation of the reserves management instrument, which limited the effectiveness of the protected area for conservation. The linkage matrix enabled the identification of possible lines of action for improving both the specific content of the Management Program and its implementation regarding wildlife use. Based on a) the results of the linkage matrix in LPBR, b) the objectives of biosphere reserves aimed at conservation and development, and c) the requirement for biosphere reserves to implement an official management instrument, we highlight the scope of applicability and the contribution of our analysis tool, which offers a means for approaching the social linkage of biosphere reserves not only in Mesoamerica but around the world.

Effects of Spatial Patch Characteristics and Landscape Context on Plant Phylogenetic Diversity in a Naturally Fragmented Forest

Phylogenetic diversity is a reliable predictor of taxonomic and functional diversity and of biodiversity option value. During forest fragmentation, forest patches that vary in size, degree of isolation, and shape are formed. Identifying the spatial characteristics of forest remnants that maximize phylogenetic diversity could be useful to conservationists when prioritizing areas to be protected if resources are limited. In this study, we assessed whether spatial patch characteristics (size, edge density, and shape) and the context of the patch in the surrounding landscape (i.e., isolation degree) affect plant phylogenetic diversity in 19 naturally shaped forest patches. Owing to the age of the forest patches, the study system allowed us to assess the long-term effects of spatial variables on phylogenetic diversity. We found that patch size has a positive effect on phylogenetic diversity, presumably because environmental heterogeneity and niche opportunities are greater in bigger patches. Also, phylogenetic diversity was positively affected by edge density. The convergent evolution of traits which confer tolerance to prevailing edge conditions in phylogenetically distant species may explain this result. We suggest that patch size is a reliable predictor of plant phylogenetic diversity and could be used as a prioritization criterion in conservation strategies, at least in the study area.