27 research outputs found
Contrasting patterns in leaf traits of Mediterranean shrub communities along an elevation gradient: measurements matter
No full textWe assessed the changes in community-weighted mean (CWM) and variability of specific leaf area (SLA) and leaf area (LA) of different Mediterranean shrub communities along an elevation gradient in the island of Sardinia (Italy). Furthermore, we explored the relative contribution of species turnover and intraspecific variation to shifts in CWM values along the gradient. Forty sampling units (5 × 5 m) were selected in a probabilistic way along a 1300 m elevation gradient which crossed four thermotypes (thermometric belts). Leaf traits were measured in each sampling unit. ANOVA and a trend test for monotonic changes in variance were used to assess, respectively, CWM differences and variability in both the leaf traits across thermotypes. Variance decomposition of CWM values was used to identify the role of inter- and intraspecific variation. SLA and LA responded differently along the studied gradient in terms of abundance-weighted mean values and variability: CWM of SLA showed the lowest values in the driest thermotype, while LA in the more humid one; SLA variability showed a significant increasing trend with increased water availability, while LA variability did not show any pattern. The contribution of intraspecific trait variation was significant for both the leaf traits, but higher for SLA, where negative covariation between inter- and intraspecific variation was detected. We highlight the importance of simultaneously considering measurements of both leaf traits to understand the functional response of communities in Mediterranean environments. Moreover, neglecting intraspecific variation in leaf traits, even along steep gradients with relevant species compositional changes, can result in the underestimation of the amount of trait variation in response to environmental changes
The Flora of Greater San Quintín, Baja California, Mexico (2005–2010)
No full textThe plants of San Quintín (Baja California, Mexico) were documented through intensive fieldwork and collection of herbarium specimens to create a checklist of species. The region is located near the southernmost extent of the California Floristic Province, and the flora is influenced by the adjacent desert to the south. A total of 435 plant taxa were documented, of which 82% are native plants. Almost one in three native plant taxa in Greater San Quintín is a sensitive species, here documented as rare and/or locally endemic, and many taxa have yet to be evaluated fully for rarity and threats. Four major habitats were identified, and a checklist is presented for each. Shell middens and vernal pools represent micro-habitats with unique species that also warrant conservation consideration. All habitats in Greater San Quintín are threatened by human activity, and agricultural water use practices are unsustainable. There is a pressing need for conservation of the natural areas that remain in this unique but heavily impacted region. The El Socorro Dunes and the volcanic bay are of particular conservation value with several narrowly endemic taxa. As a transitional area in a global biodiversity hotspot, Greater San Quintín is home to many species on the edge of their ranges and may be of critical importance to biodiversity conservation in a changing climate
The San Quintín Kangaroo Rat is Not Extinct
No full textThe San Quintín kangaroo rat (Dipodomys gravipes) is a medium-sized kangaroo rat restricted to a stretch of coastal habitat from San Telmo to El Rosario, Baja California, Mexico. Agriculture in the San Quintín area began in 1891 when British farmers converted parts of the landscape to agriculture. Now, much of the preferred habitat in the documented range of the species has been converted to agriculture. Dipodomys gravipes has a high affinity for flat terrain and is intolerant of cultivation. As a result of extensive and profound habitat alteration by agriculture, D. gravipes has been listed as endangered by the Mexican government. Since then, and given the lack of further captures, biologists and conservationists have feared the species could be extinct. However, Tremor and Vanderplank captured four specimens on 4 July 2017 on Mesa Agua Chiquita near San Quintín
Resources for Humans, Plants and Animals: Who Is the Ruler of the Driver? And: Can Resource Use Explain Everything?
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Relict inland mangrove ecosystem reveals Last Interglacial sea levels
No full textClimatic oscillations during the Pleistocene played a major role in shaping the spatial distribution and demographic dynamics of Earth's biota, including our own species. The Last Interglacial (LIG) or Eemian Period (ca. 130 to 115 thousand years B.P.) was particularly influential because this period of peak warmth led to the retreat of all ice sheets with concomitant changes in global sea level. The impact of these strong environmental changes on the spatial distribution of marine and terrestrial ecosystems was severe as revealed by fossil data and paleogeographic modeling. Here, we report the occurrence of an extant, inland mangrove ecosystem and demonstrate that it is a relict of the LIG. This ecosystem is currently confined to the banks of the freshwater San Pedro Mártir River in the interior of the Mexico-Guatemala El Petén rainforests, 170 km away from the nearest ocean coast but showing the plant composition and physiognomy typical of a coastal lagoon ecosystem. Integrating genomic, geologic, and floristic data with sea level modeling, we present evidence that this inland ecosystem reached its current location during the LIG and has persisted there in isolation ever since the oceans receded during the Wisconsin glaciation. Our study provides a snapshot of the Pleistocene peak warmth and reveals biotic evidence that sea levels substantially influenced landscapes and species ranges in the tropics during this period
Global endemics-area relationships of vascular plants
No full textEndemics–Area Relationships (EARs) are fundamental in theoretical and applied biogeography for understanding distribution patterns and promoting biodiversity conservation. However, calculating EARs for vascular plant species from existing data is problematic because of biased knowledge of endemic species distributions and differences between taxonomies. We aimed to overcome these challenges by developing a new standardized global dataset based on expert knowledge to produce a set of global EARs. We developed a nested circle design, with grain sizes of 10 4 , 10 5 , 10 6 , 10 7 , and 10 8 km 2 , respectively, and a global distribution of plots based on a stratified random scheme. The number of vascular plant species endemic to each circle was then estimated independently by five experts randomly chosen from a pool of 23, as both a minimum and a maximum value (lower and upper bounds of the estimation), taking into account the limitations of current knowledge and varied species concepts in existing taxonomies. This procedure resulted in a dataset of 3000 expert estimates. Based on the data, we produced three global EARs for endemic species richness using minimum, maximum and average estimates. As a validation, we used all three models to extrapolate to the entire world, producing estimates of 284,493 (minimum), 398,364 (maximum)and 312,243 (average)vascular plant species. These figures conform to the range of taxonomists’ estimates. From the models, we calculated the average area needed to harbour a single endemic species as 12,875 km 2 (range 9675–20,529). The global vascular plant EARs we calculated represent the first standardized, quantitative expectations of plant endemism at any given scale (sampling unit size). These EARs allow us to provide a clear answer to a long-standing but elusive biogeographical question: how to assess whether any area on the surface of the Earth is rich or poor in endemics relative to the average
