Marginal Habitats Research Articles

The development of an in vitro floral culture transformation system for quinoa

AbstractBecause of its high-quality seed protein and ability to thrive in marginal habitats, Chenopodium quinoa has been identified as an important emerging grain crop for global food security. However, the lack of an efficient and robust transformation system has been a barrier for conducting the advanced genetic studies needed to better understand and improve the species for agronomic traits. Here we present a novel transformation system based on Agrobacterium-mediated transformation of in vitro floral culture. Quinoa floral cultures were established from inflorescences that naturally formed on plants grown in vitro. When placed on a cytokinin-containing medium, chopped inflorescences rapidly generated highly meristematic floral cultures, primarily composed of floral buds, flowers at various developmental stages, inflorescence shoots, and leafy structures. Transformation of these cultures with Agrobacterium carrying selectable and visual markers (NPTII and GUS) produced independent, stably transformed meristematic cultures resistant to paromomycin after an extended selection period (about 3 mo with sub-culture occurring every 15 d). Transformation frequency was about 20% and was calculated as the number of independent transformed events per initial number of floral culture explants used for transformation. In vitro flowers and inflorescences from putative transgenic events self-pollinated naturally and produced viable seeds that germinated without dormancy. We also demonstrated that flowering shoots could be successfully grafted onto wild rootstock to increase the number of seeds generated from T0 floral shoots. Molecular and phenotypic analysis of the progeny confirmed that the transgenes were stably integrated and inherited according to expected Mendelian ratios.

Landscape genetics of spruce grouse at the trailing edge of the boreal forest

Populations on the periphery of a species range generally occupy marginal or less continuous habitat and can have greater extinction risk than populations in the range‐center. For climate‐sensitive populations on the trailing edge of a species' distribution (i.e. low latitude or low elevation), the effects of climate change are expected to compound these threats, increasing the vulnerability of these populations. The spruce grouse Canachites canadensis is a boreal forest specialist that is expected to experience range contraction at the trailing edge of its range due to climate change. In this study, we investigated the genetic structure, genetic diversity, and connectivity of spruce grouse in Minnesota, along the southeastern range limit in the United States. Clustering algorithms and genetic diversity indices suggested a single continuous population occurred throughout northern Minnesota. We detected no signatures of recent inbreeding or population bottlenecks. We used maximum likelihood population effects modeling and identified coniferous forest land cover and lower average spring temperatures as predictors of gene flow. We used two approaches based on circuit theory to map the potential for gene flow and identified regions of consistently high gene flow in the northwest and northeast of the study area. Omniscape, which incorporated additional parameters representing the likely origins of dispersers and the maximum dispersal distance, suggested a more continuous gene flow landscape than did Circuitscape. Our work highlights the current genetic integrity of one of the largest populations of the eastern subspecies of spruce grouse C. c. canadensis in the United States, identifies key landscape attributes for functional connectivity, and demonstrates complementary approaches of Circuitscape and Omniscape for gene flow mapping.

Direct and indirect effects of climate and seed dynamics on the breeding performance of a seed predator at the distribution edge.

Marginal populations usually have low densities and are considered to be particularly vulnerable to environmental stochasticity. Using data collected in nest boxes, we analyzed the breeding performance of the edible dormouse (Glis glis), an obligate hibernating rodent and a seed predator in deciduous forests, in two populations at the distribution range's edge. Despite being only 20 km apart from each other, Montseny is a large patch of mixed deciduous forests (oaks and beech), whereas Montnegre would be the harshest habitat, that is, a small, isolated patch with only oaks. First, we studied the differences in climate and tree cover change in the two populations. Second, we analyzed the direct and indirect roles of local climate conditions and seed availability on breeding performance over 10 years in each population. Finally, we explored the influence of tree cover change on the occupancy dynamics in the two populations. Our results showed contrasting responses between populations: in Montseny, asynchronous seed production between oaks and beech precluded skip breeding, and breeding performance increased with seed availability. Furthermore, dormice in Montseny may use pollen production to anticipate the amount of beech nut resources and adjust their breeding effort. Boxes showed higher occupancy and colonization and fewer extinctions in Montseny than in Montnegre, where seed availability did not drive breeding performance. Results from Montnegre suggest that skip breeding was an adaptive response to a more pulsed, harsher environment. Here, females produced a similar number of pups than at Montseny. Long-term studies dealing with population responses in marginal habitats can lead to a deeper understanding of the capacities of organisms to adapt to harsh environments. Although local adaptation is frequently documented across various taxa, studies at the distribution edge may shed light on our still limited comprehension of the underlying mechanisms responsible for its occurrence.

Genomic data reveals habitat partitioning in massive Porites on Guam, Micronesia

Corals in marginal reef habitats generally exhibit less bleaching and associated mortality compared to nearby corals in more pristine reef environments. It is unclear, however, if these differences are due to environmental differences, including turbidity, or genomic differences between the coral hosts in these different environments. One particularly interesting case is in the coral genus Porites, which contains numerous morphologically similar massive Porites species inhabiting a wide range of reef habitats, from turbid river deltas and stagnant back reefs to high-energy fore reefs. Here, we generate ddRAD data for 172 Porites corals from river delta and adjacent (<0.5 km) fore reef populations on Guam to assess the extent of genetic differentiation among massive Porites corals in these two contrasting environments and throughout the island. Phylogenetic and population genomic analyses consistently identify seven different clades of massive Porites, with the two largest clades predominantly inhabiting either river deltas or fore reefs, respectively. No population structure was detected in the two largest clades, and Cladocopium was the dominant symbiont genus in all clades and environments. The perceived bleaching resilience of corals in marginal reefs may therefore be attributed to interspecific differences between morphologically similar species, in addition to potentially mediating environmental differences. Marginal reef environments may therefore not provide a suitable refuge for many reef corals in a heating world, but instead host additional cryptic coral diversity.

Seagrass recovery trajectories and recovery potential in relation to nutrient reduction

Abstract Seagrass recovery has been reported across the globe where previously eutrophied waters have become less nutrient‐rich. In the European Wadden Sea, different recovery trajectories were found after riverine nutrient loads decreased, namely full, temporary and no recovery. We compiled intertidal seagrass presence (Zostera noltei and Z. marina) and eutrophication data for 1930–2020, to relate the seagrass trajectories and regional eutrophication differences to riverine nutrient loads, and inferred prospects for seagrass recovery. Seagrass fully recovered in the less eutrophic North Frisian region. The recovery trajectory was tightly coupled to riverine nutrient load reduction. Relative seagrass area (meadow area/region area) dropped from 10% prior to eutrophication to 2% during the eutrophication peak, increased to 7% during the nutrient reduction period and subsequently expanded to 13%. Colonization of marginal habitats was observed, indicating propagule spillover from neighbouring meadows. The more eutrophic southern regions showed no or only temporary seagrass recovery. Prospects for (limited) recovery are good in only two out of four southern regions, provided that riverine nutrient loads are further reduced by ~40% (reference: 2010–2017). Without this reduction, seagrasses may only temporarily recover and will remain vulnerable to erratic disturbances like macroalgae accumulation or storms. Historical evidence and application of habitat suitability models suggest that the potential relative seagrass area in the southern regions is low: less than 0.2% in the western Dutch region and maximum 2.4% in the Ems‐Jade region. Synthesis and applications. Within a large seascape (15,000 km2) the least eutrophicated region showed seagrass recovery upon nutrient reduction. We translated the critical riverine nutrient loads for this recovery, via regional eutrophication indicators, to loads that may enable a sustained recovery in the other regions. This technique is applicable in other complex systems, provided sufficient historical data are available. Propagule spillover exerts a positive feedback at metapopulation scale leading to acceleration of recovery. Occupied and potential seagrass habitat (e.g. assessed by the maximum recorded area in the past) are thus important landscape selection criteria for restoration, particularly when eutrophication is not yet sufficiently reduced.

Environmental impact on marginal coastal benthic communities within the Jeju Island, South Korea temperate transition zone

Aim of studyMarine climatic transition zones are boundary areas of major climate zones, here the boundary between the subtropical and temperate zones. They present areas containing high abundance of organisms living at the limit of their physiological tolerance. These marginal populations are particularly sensitive to changes in their environment. As such, marine climatic transition zones are excellent natural playgrounds for climate change-related hypothesis testing, especially with respect to marine habitat response to ocean warming. The marginal biogenic habitats around Jeju Island, South Korea, which lies within the temperate transition zone, have gradually changed from macroalgal-dominated to hard coral-dominated habitats. Understanding the specific abiotic environmental factors that influence the distribution of the marginal populations in temperate transition zones (i.e., species at their occurrence limit) is crucial to predicting and managing temperate zone habitat changes caused by climate change. This study aims to identify the specific abiotic environmental factors that contribute to explaining the current spatial distribution of the declining temperate and expanding subtropical foundation species in Jeju waters.MethodsCoverage and composition of sessile benthic communities were determined by photo-quadrat analysis at two depths (10 m and 15 m) at three sites along the island’s south, east, and north coasts in May and November 2022. Divergences in community composition between sites were characterized in light of ten quantitative environmental parameters.ResultsOur results show that sessile foundation communities vary significantly at different sites around the island. While the south is defined by high-latitude hard corals, predominately Alveopora japonica, the east is defined by the temperate canopy-forming macroalga Ecklonia cava, and the north is characterized by coralline algae. Winter sea surface temperature, water transparency, nutrient concentration, and water movement were statistically the most impactful environmental factors determining which foundation species constitute each distinct benthic community.ConclusionThis study provides valuable baseline information on the impacts of abiotic environmental factors on marine sessile communities in a temperate transition zone.

Assessing the potential risks of climate change on the natural capital of six countries resulting from global warming of 1.5 to 4 °C above pre-industrial levels

We present the results from a new framework providing an assessment of how climate change risks to natural capital accrue with warming of 1.5–4 °C in six countries (China, Brazil, Egypt, Ethiopia, Ghana, and India). Unlike typical biodiversity and climate change studies, this assessment also considers landcover and population changes across a range of 17 ecosystem services. The potential impacts of climate change (alone) on natural capital at 1.5 °C is greatest in Brazil and least in Ghana. However, when population and landcover change are included, areas projected to be at high natural capital risk begin to accrue by 1.5 °C in all countries. By 2 °C, Ethiopia and Ghana show increasing areas at high risk, even though they are at low risk owing to climate alone. Thus, current impacts to biodiversity and ecosystem services and changes in potential demand coupled with warming exceed changes projected by climate alone. However, this also indicates that there is adaptation potential, especially with warming of < 2 °C, to reduce risk through restoring habitat. At lower levels of warming, targeted restoration of marginal agricultural habitats would increase the bank of natural capital for use by people and provide support for remaining agricultural lands. By 3 °C, the adaptation potential from restoration is substantially less: < 1% in Brazil, India and Egypt; 7–8% in China and Ethiopia; but still 26% in Ghana. This indicates that restoration as an adaptation option for biodiversity, and thus, natural capital, rapidly decreases with increasing temperatures. By 2100, factoring in population change (SSP2), current ecological footprint, and current landcover, even with only 1.5 °C warming, large parts of Brazil, eastern China, most of Egypt, much of Ethiopia, southwestern Ghana (except for protected areas), and most of India are at high to extreme natural capital risk with an adaptation deficit potentially equating to a soft adaptation limit.

A grazer's niche edge is associated with increasing diet diversity and poor population performance.

The core-periphery hypothesis predicts niche cores should be associated with greater survivorship, reproductive output and population performance rates than marginal habitats at niche edges. However, there is very little empirical evidence of whether niche centrality influences population trends in animals. Using the Cape mountain zebra (Equus zebra zebra) as a model system, we evaluated whether niche centrality is associated with population trends, resource availability and diet across a core-periphery gradient. Population growth rates and density progressively declined towards niche peripheries. Niche peripheries were resource-poor and Cape mountain zebra consumed more phylogenetically diverse diets dominated by non-grass families. In core habitats they consumed grass-rich diets and female reproductive success was higher. This combination of spatial niche modelling and functional ecology provides a novel evaluation of how bottom-up resource limitation can shape species distributions, population resilience and range change and can guide conservation management.

Predicted Climate Change Impacts on Distribution and Habitat Structure of Forest Ungulates in Southwest China

Climate change will impact the distribution of species and their preferred habitat, thereby influencing the ecological processes intrinsic to these species. To investigate these phenomena, we analyzed the habitat distribution, structure, and connectivity of 6 forest ungulate species in Southwest China under current and future climate scenarios. Habitat projections indicate that forest ungulates will migrate to the southwest at higher elevations and the northwest at higher latitudes and elevations in the study area under climate change. The extent to which climate change affects the 6 forest ungulates is quite different. By 2050, there will still be a certain range of habitats for migration in the study area, but the habitat quality of species will have decreased to varying degrees after migration. By 2070, most forest ungulates will begin to experience significant habitat loss and habitat quality decline. The migration of species habitat also leads to a change in species habitat structure. Habitat landscape quality declines for most forest ungulate species. The loss of patches at the junction habitat has a huge impact on species habitat connectivity. The number and distance of corridors between the marginal habitat patches and the core habitat patches increase to a certain extent. To better achieve biodiversity conservation, we should strengthen the restoration and connectivity management of fragmented habitats to protect and restore the current habitats of species. Examples include the management of specific key areas and the establishment of large-scale integrated protected areas such as the Giant Panda National Park.

Rapid population decline in McKay’s Bunting, an Alaskan endemic, highlights the species’ current status relative to international standards for vulnerable species

Abstract The McKay’s Bunting (Plectrophenax hyperboreus) is endemic to Alaska, breeds solely on the remote and uninhabited St. Matthew and Hall islands (332 km2) in the central Bering Sea, and is designated as a species of high conservation concern due to its small population size and restricted range. A previous hypothesized population estimate (~2,800 to 6,000 individuals) was greatly increased (~31,200 individuals) after systematic surveys of the species’ entire breeding range in 2003, establishing McKay’s Bunting as one of the rarest passerines in North America. In 2018, we replicated the 2003 surveys and used density surface models to estimate breeding season densities, distributions, and population change over the intervening time period. Our results indicate that the McKay’s Bunting population declined by 38% (95% CI: 27 to 48%) from ~31,560 to 19,481 individuals since 2003. Spatial model predictions showed no areas with an increase of birds on either St. Matthew or Hall islands but revealed declines across 13% (42 km2) of St. Matthew Island. Declines disproportionately occurred both in marginal habitats with reduced rocky nesting substrate and in high-density hotspots along the coast of St. Matthew Island. The total area occupied by breeding adults decreased by 8%, and high-density hotspots shifted inland from the coast of St. Matthew Island to higher elevations on both islands, the latter potentially responses to exceptionally warm weather and reduced spring snow cover in 2018. Additionally, we observed low numbers of predators and interspecific competitors in 2018, suggesting that these did not cause the decline. Our findings indicate that McKay’s Bunting meets international standards for elevating its conservation status from Least Concern to Endangered based on the International Union for Conservation of Nature Red List of Threatened Species ranking criteria. Additional population monitoring and studies to identify the causal mechanisms of the recent population decline of this rare species could assist future population assessments.

Biodiversity conservation in Myanmar's coastal wetlands: Focusing on saltwater crocodile habitats and connectivity

Landscape-level conservation strategies are needed to protect the saltwater crocodile population and habitats in Myanmar. Identifying the remaining habitats and movement corridors is essential due to population decline across coastal regions and insufficient habitat coverage, even within protected areas. This study predicts the distribution of habitats and creates low-resistance corridors that facilitate movement across the landscape. Occurrence dataset encompassing a 20-year period (1999–2019) was used incorporating records gathered from the Global Biodiversity Information Facility—GBIF, crocodile counting reports from the Meinmahla Kyun wildlife sanctuary of Myanmar, and recent spotlight and camera-trap surveys. Using landscape connectivity tools, structural compositions of habitat classes were determined, and habitat patches were delineated to simulate the least-cost corridor and dispersal pathways. Two patches in Rakhine, two in Ayeyarwady and Yangon, one in Mon, and two in Tanintharyi, were identified that include 1247 km2 of core suitable habitat areas. The Ayeyarwady Delta exhibits a plethora of suitable habitats, while the Rakhine and Tanintharyi regions have higher marginal habitats that are largely unprotected. Only 12 % of the extent of occurrence of saltwater crocodiles are suitable habitats with a high potential for occupancy. Habitats are highly fragmented and four bottlenecks are identified to assist population connectivity in those fragmented patches. Despite notable challenges in ensuring connectivity to restore populations across the habitat patches, we highlighted connectivity as the foundation for establishing an ecological network of Myanmar's coastal habitats, leveraging the saltwater crocodile as an umbrella species for the region's coastal wetlands, and identifying key areas for enhanced protection.

Spatial patterns of reproduction suggest marginal habitat limits continued range expansion of black bears at a forest-desert ecotone.

Investigating spatial patterns of animal occupancy and reproduction in peripheral populations can provide insight into factors that form species range boundaries. Following historical extirpation, American black bears (Ursus americanus) recolonized the western Great Basin in Nevada from the Sierra Nevada during the late 1900s. This range expansion, however, has not continued further into the Great Basin despite the presence of additional habitat. We aimed to quantify whether reduced reproduction toward the range edge contributes to this range boundary. We analyzed black bear detections from 100 camera traps deployed across black bear distribution in western Nevada using a multistate occupancy model that quantified the probability of occupancy and reproduction (i.e., female bears with cubs occupancy) in relation to changes in habitat type and habitat amount toward the range boundary. We detected a strong effect of habitat amount and habitat type on the probability of black bear occupancy and reproduction. At similar levels of landscape-scale habitat amount (e.g., 50%), estimated probability of occupancy for adult bears in piñon-juniper woodlands near the range boundary was 0.39, compared to ~1.0 in Sierra Nevada mixed-conifer forest (i.e., core habitat). Furthermore, estimated probability of cub occupancy, conditional on adult bear occupancy, in landscapes with 50% habitat was 0.32 in Great Basin piñon-juniper woodlands, compared to 0.92 in Sierra Nevada mixed-conifer forest. Black bear range in the western Great Basin conforms to the center-periphery hypothesis, with piñon-juniper woodland at the range edge supporting ecologically marginal habitat for the species compared to habitat in the Sierra Nevada. Further geographic expansion of black bears in the Great Basin may be limited by lower occupancy of reproducing females in piñon-juniper woodland. Center-periphery range dynamics may be common in large carnivore species, as their dispersal ability allows them to colonize low-quality habitat near range edges.

Traditional landscape elements are key to the threatened Ortolan Bunting Emberiza hortulana in its Italian stronghold

ABSTRACT Capsule Cultural landscapes with Tamarisk Tamarix gallica rows, marginal habitats and crop heterogeneity promote the occurrence of Ortolan Buntings Emberiza hortulana in the Marche region, a key area for the species’ conservation in Italy. Aims To evaluate the land-use determinants of the occurrence of the Ortolan Bunting, a species strikingly declining in recent decades. Methods Within the Marche region, the Italian stronghold of the species, we surveyed 20 plots in the hilly belt of Pesaro-Urbino province, and recorded different potential land-cover drivers of the occurrence of Ortolan Buntings. We modelled habitat selection according to environmental variables measured in the field at an equal number of territory and control sites, using generalized linear models. Results We found 104 territories of Ortolan Buntings. Different groups of predictors (crop cover, marginal habitats, other land-uses) were similarly important; positive drivers of the species’ occurrence were the covers of cereal, dead trees, pure and mixed Tamarisk rows, other crops, sunflower, and reeds; covers of broom had a quadratic effect, while negative effects were found with seminatural grassland, paved roads, and isolated shrubs. The disappearance of cultural landscapes, which is ongoing in many European areas, resulted in the loss of elements typically found in low-intensity farming systems and of particular importance for the species. Tamarisk rows may provide multiple benefits, offering song posts and potential nesting sites close to the ground, and their abundance in the Marche region could contribute to explain why Ortolan Buntings are locally more common there, compared to other Italian regions. Conclusions The maintenance of Tamarisk rows, marginal habitats and crop heterogeneity are key measures needed to support Ortolan Bunting populations.

Enhanced and asymmetric signatures of hybridization at climatic margins: Evidence from closely related dioecious fig species

Hybridization plays a significant role in biological evolution. However, it is not clear whether ecological contingency differentially influences likelihood of hybridization, particularly at ecological margins where parental species may exhibit reduced fitnesses. Moreover, it is unknown whether future ecosystem change will increase the prevalence of hybridization. Ficus heterostyla and F. squamosa are closely related species co-distributed from southern Thailand to southwest China where hybridization, yielding viable seeds, has been documented. As a robust test of ecological factors driving hybridization, we investigated spatial hybridization signatures based on nuclear microsatellites from extensive population sampling across a widespread contact range. Both species showed high population differentiation and strong patterns of isolation by distance. Admixture estimates exposed asymmetric interspecific gene flow. Signatures of hybridization increase significantly towards higher latitude zones, peaking at the northern climatic margins. Geographic variation in reproductive phenology combined with ecologically challenging marginal habitats may promote this phenomenon. Our work is a first systematic evaluation of such patterns in a comprehensive, latitudinally-based clinal context, and indicates that tendency to hybridize appears strongly influenced by environmental conditions. Moreover, that future climate change scenarios will likely alter and possibly augment cases of hybridization at ecosystem scales.

Threatened fauna protections compromised by agricultural interests in Australia

AbstractAustralia is a global leader in land clearing and biodiversity loss. The overwhelming majority of land clearing within Australia and, globally, is driven by agricultural conversion. The importance of agricultural lands also leads to the concentration of habitat protection in landscapes that do not support productive land uses, which might contribute to species conservation in marginal habitat. Using an integrated agricultural capability map and threatened vertebrate fauna range maps, we show that observed biases in protected area location have varied impacts at the species level. Specifically, threatened vertebrate fauna with habitat capable of supporting high‐value productive lands received less protection and experienced greater habitat loss. Similarly, almost all species assessed received protection in the portions of their ranges less conducive to productive land uses. Finally, we identify regions of Australia at risk of future land clearing and the species likely to bear the brunt of the impacts. Our results demonstrate the importance of protecting land capable of supporting productive uses to conserve the most affected threatened species.

Why did foraging, horticulture and pastoralism persist after the Neolithic transition? The oasis theory of agricultural intensification.

Despite the global spread of intensive agriculture, many populations retained foraging or mixed subsistence strategies until well into the twentieth century. Understanding why has been a longstanding puzzle. One explanation, called the marginal habitat hypothesis, is that foraging persisted because foragers tended to live in marginal habitats generally not suited to agriculture. However, recent empirical studies have not supported this view. The alternative but untested oasis hypothesis of agricultural intensification claims that intensive agriculture developed in areas with low biodiversity and a reliable water source not reliant on local rainfall. We test both the marginal habitat and oasis hypotheses using a cross-cultural sample drawn from the 'Ethnographic atlas' (Murdock 1967 Ethnology 6, 109-236). Our analyses provide support for both hypotheses. We found that intensive agriculture was unlikely in areas with high rainfall. Further, high biodiversity, including pathogens associated with high rainfall, appears to have limited the development of intensive agriculture. Our analyses of African societies show that tsetse flies, elephants and malaria are negatively associated with intensive agriculture, but only the effect of tsetse flies reached significance. Our results suggest that in certain ecologies intensive agriculture may be difficult or impossible to develop but that generally lower rainfall and biodiversity is favourable for its emergence. This article is part of the theme issue 'Evolutionary ecology of inequality'.

Habitat quality affects the social organization in mouse lemurs (Microcebus griseorufus)

Species can either maintain a certain social organization in different habitats or show different social organizations in similar habitats. The reasons underlying this variability are not always clear but might have consequences for population dynamics, especially under changing environmental conditions. Among mammals, the primate genus Microcebus lives in small groups of closely related females, derived from female philopatry and dispersed males, as illustrated by the well-studied Microcebus murinus. Here, we studied the genetic structure of a population of the congeneric Microcebus griseorufus, inhabiting three adjacent habitats with different resource availabilities. In order to learn more about the plasticity of the species’ social organization under these different conditions, we analyzed the spatial arrangement of mitochondrial haplotypes of 122 individuals. The study revealed high haplotype diversity and a pronounced difference in spatial distribution between the sexes. Females exhibited spatial aggregation of haplotypes, suggesting a system of female philopatry and matrilines, similar to M. murinus. Male haplotypes were dispersed, and males were more likely to carry rare haplotypes, indicating higher dispersal activity. These findings hint towards the unity of the social organization across the genus Microcebus, suggesting a phylogenetic origin of the social organization. Yet, with decreasing resources, the clustering of female haplotypes declined and approached a random distribution in the marginal habitat, with cluster sizes correlating with resource availability as predicted by the socioecological model. Our study supports the notion that social organization is shaped by both phylogenetic origin and ecological conditions, at least in these small primates.Significance statementImpacts of habitat degradation are mostly described in terms of changes in population densities in relation to the reduction of resources. This neglects the possible effects of altered social organizations due to declining resources or population densities. Using a genetic sampling of three subpopulations of mouse lemurs in Madagascar along a gradient of food availability up to the limit of the species’ ecological tolerance, we show that their social organization consisting of spatial clusters of closely related females and overdispersed males converges towards random spatial distributions of both sexes with declining food availability.

Drought resilience of Mongolian Scotch pine (Pinus sylvestris var. mongolica) at the southernmost edge of its natural distribution: A comparison of natural forests and plantations

Global warming has increased the frequency and intensity of climatic drought events, intensifying the vulnerability of forest ecosystems, especially at the marginal habitats. The resilience of marginal forests to drought stress is a critical issue of sustainable forest management. In this study, the post-drought resilience of natural and planted populations of Mongolian Scotch pine (Pinus sylvestris var. mongolica), the most widely planted conifers in the semiarid temperate China, was compared at the southernmost of the species’ natural range. Three drought events in this region were identified in time series of SPEI data during last 40 years. i.e. in 1986–1987, 2003–2004, and 2007–2008. We calculated the individual-level detrended Basal Area Index before, during, and after the three drought events, and compared the resistance (Rt), recovery (Rc), and resilience (Rs) of natural and planted populations to the droughts. The results showed a negative relationship between Rt and Rc. Both natural and planted Mongolian Scotch pine forests showed positive Rs and could revert to their pre-drought growth levels within 3 years after the most severe drought. Nevertheless, we found a more stable Rs in natural forests than plantations to drought events of different severities, and a high pre-drought growth could weaken the Rs for both natural forests and plantations. The pre- and post-drought precipitation levels were both critical for the Rt and Rc of Mongolian Scotch pine to a drought. Forest age significantly reduced Rs and population density weakened Rc in natural forests. Our results revealed the joint influence of climate, site, and population characteristics on the resilience components of Mongolian Scotch pine to drought stress in the marginal habitats, which provided references for plantation planning and sustainable forest management in arid regions.

Ecological limits of the highland forest in the Chimborazo Fauna Production Reserve using multivariate statistical techniques; Basis for the economic valuation of its environmental services

Among the main terrestrial habitats are forests that present great diversity and endemism, despite their importancedue to the socioeconomic and ecological benefits they provide to human populations, they are vulnerable to modifications generatedby global changes de-rived from anthropogenic activities, and climate change that affect this important eco-system, Mitigating the effects of this entails a great responsibility that must be based on knowledge. To understand the dynamics of the evergreen forest plant formation of the páramo in the Chimborazo Fauna Production Reserve, we set out to characterize these ecosystems with respect to various environmental and forest variables through different multivariate statistical techniques. The factors evaluated were structure and composition. Forest information was obtained in 12 plots (with a total area of 4.32 ha). Univariate de-scriptive statistics allowed to determine the optimal and marginal habitat, the cluster analysis determined three similar groups according to forest characteristics, the principal components analysis showed that temperature (BIO 7) and precipitation (BIO 14) are the main variables that explain the distribution of forest species in the areas, the analysis of multiple correspondences allowed to determine that the relicts of evergreen forest of the páramo located in the parish Pilahuin contain forest species with optimal conservation characteristics.

Tetrasporophytic bias coupled with heterozygote deficiency in antarctic plocamium sp. (florideophyceae, rhodophyta).

Meiosis and syngamy generate an alternation between two ploidy stages, but the timing of these two processes varies widely across taxa, thereby generating life cycle diversity. One hypothesis suggests that life cycles with long-lived haploid stages are correlated with selfing, asexual reproduction, or both. Though mostly studied in angiosperms, selfing and asexual reproduction are often associated with marginal habitats. Yet, in haploid-diploid macroalgae, these two reproductive modes have subtle but unique consequences whereby predictions from angiosperms may not apply. Along the western Antarctic Peninsula, there is a thriving macroalgal community, providing an opportunity to explore reproductive system variation in haploid-diploid macroalgae at high latitudes where endemism is common. Plocamium sp. is a widespread and abundant red macroalga observed within this ecosystem. We sampled twelve sites during the 2017 and 2018 field seasons and used ten microsatellite loci to describe the reproductive system. Overall genotypic richness and evenness were high, suggesting sexual reproduction. Eight sites were dominated by tetrasporophytes, but there was strong heterozygote deficiency, suggesting intergametophytic selfing. We observed slight differences in the prevailing reproductive mode among sites, possibly due to local conditions (e.g., disturbance) that may contribute to site-specific variation. It remains to be determined whether high levels of selfing are characteristic of macroalgae more generally at high latitudes, due to the haploid-diploid life cycle, or both. Further investigations of algal life cycles will likely reveal the processes underlying the maintenance of sexual reproduction more broadly across eukaryotes, but more studies of natural populations are required.