Rafael F. del Castillo

Toward Integrated Analysis of Human Impacts on Forest Biodiversity: Lessons from Latin America

Although sustainable forest management (SFM) has been widely adopted as a policy and management goal, high rates of forest loss and degradation are still occurring in many areas. Human activities such as logging, livestock husbandry, crop cultivation, infrastructural development, and use of fire are causing widespread loss of biodiversity, restricting progress toward SFM. In such situations, there is an urgent need for tools that can provide an integrated assessment of human impacts on forest biodiversity and that can support decision making related to forest use. This paper summarizes the experience gained by an international collaborative research effort spanning more than a decade, focusing on the tropical montane forests of Mexico and the temperate rain forests of southern South America, both of which are global conservation priorities. The lessons learned from this research are identified, specifically in relation to developing an integrated modeling framework for achieving SFM. Experience has highlighted a number of challenges that need to be overcome in such areas, including the lack of information regarding ecological processes and species characteristics and a lack of forest inventory data, which hinders model parameterization. Quantitative models are poorly developed for some ecological phenomena, such as edge effects and genetic diversity, limiting model integration. Establishment of participatory approaches to forest management is difficult, as a supportive institutional and policy environment is often lacking. However, experience to date suggests that the modeling toolkit approach suggested by Sturvetant et al. (2008) could be of value in such areas. Suggestions are made regarding desirable elements of such a toolkit to support participatory-research approaches in domains characterized by high uncertainty, including Bayesian Belief Networks, spatial multi-criteria analysis, and scenario planning.

Forest Landscape Restoration in the Drylands of Latin America

Forest Landscape Restoration (FLR) involves the ecological restoration of degraded forest landscapes, with the aim of benefiting both biodiversity and human well-being. We first identify four fundamental principles of FLR, based on previous definitions. We then critically evaluate the application of these principles in practice, based on the experience gained during an international, collaborative research project conducted in six dry forest landscapes of Latin America. Research highlighted the potential for FLR; tree species of high socioeconomic value were identified in all study areas, and strong dependence of local communities on forest resources was widely encountered, particularly for fuelwood. We demonstrated that FLR can be achieved through both passive and active restoration approaches, and can be cost-effective if the increased provision of ecosystem services is taken into account. These results therefore highlight the potential for FLR, and the positive contribution that it could make to sustainable development. However, we also encountered a number of challenges to FLR implementation, including the difficulty of achieving strong engagement in FLR activities among local stakeholders, lack of capacity for community-led initiatives, and the lack of an appropriate institutional and regulatory environment to support restoration activities. Successful implementation of FLR will require new collaborative alliances among stakeholders, empowerment and capacity building of local communities to enable them to fully engage with restoration activities, and an enabling public policy context to enable local people to be active participants in the decision making process.

Multiple Nuclear Loci Reveal the Distinctiveness of the Threatened, Neotropical Pinus chiapensis

Pinus chiapensis is a threatened species of pine from southern Mexico and Guatemala. It was first described as a disjunct variety of P. strobus from the eastern United States and Canada. Subsequent morphological work indicates that P. chiapensis is a distinct species, but this interpretation is controversial. To explore the distinctiveness of this taxon, we sequenced three low-copy, unlinked nuclear loci in multiple accessions of P. chiapensis and its three most probable progenitors (P. ayacahuite, P. monticola, and P. strobus). Pinus chiapensis had the lowest combined nucleotide diversity of the four species (0.0031), and had only a single allele rangewide at one locus. Pinus chiapensis does not share alleles with any of the possible progenitors and all of its alleles are monophyletic at two of the three loci. At the third locus, allelic nonmonophyly is statistically indistinguishable from monophyly. While our results show that P. chiapensis is at least as distinct as the remaining three widely accepted species, determination of the most recent common ancestor is complicated by lack of allelic monophyly within potential progenitors and interlocus variability. Based on our sample of individuals and loci, P. ayacahuite appears to be the least likely progenitor, but there is no clear resolution of whether P. chiapensis is more closely related to P. monticola or P. strobus.

Ethnobotany of Ferocactus histrix and Echinocactus platyacanthus (Cactaceae) in the semiarid central Mexico: past, present and future

Ferocactus histrix and Echinocactus platyacanthus are two common barrel cacti of the semiarid highlands of Central Mexico. In pre-Columbian times, these plants were sacred, used for sacrifices, food and medicine. Today, these cacti are used in the candy industry, as medicine, as a source of food and water for goats and as ornamental plants. The floral buds and fruits ofF. histrix are consumed by the local people; the latter are sold in local markets. Until recently, the apical indument ofE. platyacanthus was used for padding and weaving. The importance of these species increases with the aridity of the land and its inadequacy for agriculture. Habitat protection and artificial propagation are needed to avoid the extinction of these species.ResumenLas biznagas Ferocactus histrix y Echinocactus platyacanthus son comunes en las regiones semiáridas del Altiplano Mexicano. En tiempos precolombianosfueron cactos sagrados que se usaban para sacrificios, como alimenta y medicina. Actualmente, estas plantas se emplean con fines medicinales y ornamentales, para la industria confitera y como fuente de alimento y agua para cabras. Los botones florales y frutos de F. histrix son consumidos localmente; estos últimos se comercializan. Hasta hace poco, el indumento apical de E. platyacanthus se usaba como relleno y se hilaba. La importancia de estas especies se incrementa en condiciones de mayor aridez y con lo inadecuado de la tierra para la agricultura y la ganadería. Es necesario proteger el hábitat y emplear técnicas de propagación artificial para evitar la extinción de estas especies.

Genetic factors associated with population size may increase extinction risks and decrease colonization potential in a keystone tropical pine

Pioneer species are essential for forest regeneration and ecosystem resilience. Pinus chiapensis is an endangered pioneer key species for tropical montane cloud forest regeneration in Mesoamerica. Human activities have severely reduced some P. chiapensis populations, which exhibited a small or null colonization potential suggesting the involvement of genetic factors associated with small populations. We explored the relationships between (i) population genetic diversity (allozymes) and population size, including sampling size effects, (ii) fitness estimates associated with colonization potential (seed viability and seedling performance) in a common environment and population size, and (iii) fitness estimates and observed heterozygosity in populations with sizes spanning five orders of magnitude. All the estimates of genetic diversity and fitness increased significantly with population size. Low fitness was detected in progenies of small populations of disturbed and undisturbed habitats. Progenies with the lowest observed heterozygosity displayed the lowest fitness estimates, which, in turn, increased with heterozygosity, but seed viability peaked at intermediate heterozygosity values suggesting inbreeding and outbreeding depression. Inbreeding depression appears to be the most immediate genetic factor in population decline. Conservation efforts should try to maintain large and genetically diverse populations, enhance gene flow by restoring connectivity between adjacent populations, and avoid genetically distant individuals.

Reproductive implications of combined and separate sexes in a trioecious population of Opuntia robusta (Cactaceae)

Opuntia robusta has hermaphroditic, dioecious, and trioecious populations. To enhance our understanding of this breeding system diversity, we compared the reproductive output of males, females, and hermaphrodites in a trioecious population using field evaluations, controlled crosses, and progeny tests. Unisexuals were fully sterile in one sex function. Hermaphrodites were fully fertile for both functions. Consistent with the sex-allocation theory, unisexuality increased the quality and quantity (in males) of the gametes of the functional sex, relative to those of hermaphrodites, probably explained by maternal and paternal effects. The increase was higher in males than in females, suggesting a more expensive female function. Theoretically, this disproportional increase is required for unisexuals to invade a hermaphroditic population with prior selfing, negligible pollen discounting, and undetectable inbreeding depression, features found in O. robusta, therefore helping to explain dioecious populations. However, in the study population, the actual seed output of females was lower and had a higher variance than that of hermaphrodites, which also reproduce through pollen. Unisexuals are unlikely to be maintained by their actual reproductive output in this pollen-limited environment. Hermaphrodites may persist in this population by producing their seeds autonomously and by reducing interspecific fertilization by prior selfing and ovule discounting.

Inbreeding depression in a zygotic algebra

We study the algebraic behavior of a three dimensional zygotic algebra in the presence of parameters 0 < s < 1 and 0 < g < 1; s for selfing and g which reflects its associated inbreeding depression. We also study the dynamics of the system for which this algebra is a model. Our methods lean towards commutative algebra and algebraic geometry and find support on the computer program Macaulay2.Our results are best understood through the geometry of a rational function of the projective plane.

Possible combined effects of climate change, deforestation, and harvesting on the epiphyte Catopsis compacta: a multidisciplinary approach

Climate change, habitat loss, and harvesting are potential drivers of species extinction. These factors are unlikely to act on isolation, but their combined effects are poorly understood. We explored these effects in Catopsis compacta, an epiphytic bromeliad commercially harvested in Oaxaca, Mexico. We analyzed local climate change projections, the dynamics of the vegetation patches, the distribution of Catopsis in the patches, together with population genetics and demographic information. A drying and warming climate trend projected by most climate change models may contribute to explain the poor forest regeneration. Catopsis shows a positive mean stochastic population growth. A PVA reveals that quasi-extinction probabilities are not significantly affected by the current levels of harvesting or by a high drop in the frequency of wet years (2%) but increase sharply when harvesting intensity duplicates. Genetic analyses show a high population genetic diversity, and no evidences of population subdivision or a past bottleneck. Colonization mostly takes place on hosts at the edges of the fragments. Over the last 27 years, the vegetation cover has being lost at a 0.028 years−1 rate, but fragment perimeter has increased 0.076 years−1. The increases in fragment perimeter and vegetation openness, likely caused by climate change and logging, appear to increase the habitat of Catopsis, enhance gene flow, and maintain a growing and highly genetically diverse population, in spite of harvesting. Our study evidences conflicting requirements between the epiphytes and their hosts and antagonistic effects of climate change and fragmentation with harvesting on a species that can exploit open spaces in the forest. A full understanding of the consequences of potential threatening factors on species persistence or extinction requires the inspection of the interactions of these factors among each other and their effects on both the focus species and the species on which this species depends.

On the possible role of nonreproductive traits for the evolution of unisexuality: Life-history variation among males, females, and hermaphrodites in Opuntia robusta (Cactaceae)

Abstract In angiosperms, dioecy has arisen in 871–5,000 independent events, distributed in approximately 43% of the flowering families. The reproductive superiority of unisexuals has been the favorite explanation for the evolution of separate sexes. However, in several instances, the observed reproductive performance of unisexuals, if any, does not seem to compensate for the loss of one of the sex functions. The involvement of fitness components not directly associated with reproduction is a plausible hypothesis that has received little attention. Life‐history traits recently recognized as predictors of plant performance were compared among males, females, and hermaphrodites of a rare trioecious Opuntia robusta population in the field, using the cladode as the study unit. Cladode mortality by domestic herbivores was common and higher in females and hermaphrodites than in males. Males, females, or both displayed lower shrinkage and higher rates of survival, growth, and reproductive frequency than hermaphrodites. Unisexuals simultaneously outperformed hermaphrodites in demographic traits known to compete for common limiting resources, such as the acceleration of reproductive maturation (progenesis) and survival. A meta‐analysis combining the outcomes of each of the analyzed life‐history traits revealed a tendency of males (d ++ = 1.03) and females (d ++ = 0.93) to outperform hermaphrodites in presumably costly demographic options. Clonality is induced by human or domestic animal plant sectioning; and males and females highly exceeded hermaphrodites in their clonality potential by a factor of 8.3 and 5.3, respectively. The performances of unisexuals in the analyzed life‐history traits may enhance their reproductive potential in the long run and their clonality potential and could explain the observed increase of unisexuality in the population. Life‐history traits can be crucial for the evolution of unisexuality, but their impact appears to be habitat specific and may involve broad ontogenetic changes.