Establishing Restoration Strategy of Eastern Oyster via a Coupled Biophysical Transport Model

For marine fish and invertebrates, larval dispersal plays a critical role in determining connections among source and sink habitats, and the lack of a predictive understanding of larval dispersal is a fundamental obstacle to the development of spatially explicit restoration plans for marine populations. We investigated larval dispersal patterns of eastern oyster in an estuary along the Northern Gulf of Mexico under different simulation scenarios of tidal amplitude and phase, river discharge, wind direction, and larval vertical migration, using a coupled biophysical transport model. We focused on the dispersal of larvae released from the commercially exploited (Cedar Point, CP) and non‐exploited (Bon Secour Bay, BSB) oyster populations. We found that high flushing rates through the dominant inlet prevented larval exchange between the commercially exploited and non‐exploited populations, resulting in negligible connectivity between them. Variations in tidal amplitude, river discharge and wind direction played a more important role in the amount of larvae retained in Mobile Bay when they are released from CP than from BSB. Under most of the scenarios, larvae from BSB were retained around the spawning area, while larvae from CP showed a predominant westward flow. Net sinking behavior of late‐stage larvae increased larval retention in the bay, but physical transport showed a higher impact in the amount of larvae retained. These findings have enhanced our understanding of larval dispersal of eastern oyster in a wide, shallow estuarine system, and been used to establish spatially explicit strategies for oyster restoration in the Mobile Bay system, Alabama.     

Ecosystem Services from Keystone Species: Diversionary Seeding and Seed‐Caching Desert Rodents Can Enhance Indian Ricegrass Seedling Establishment

Seeds of Indian ricegrass (Achnatherum hymenoides), a native bunchgrass common to sandy soils on arid western rangelands, are naturally dispersed by seed‐caching rodent species, particularly Dipodomys spp. (kangaroo rats). These animals cache large quantities of seeds when mature seeds are available on or beneath plants and recover most of their caches for consumption during the remainder of the year. Unrecovered seeds in caches account for the vast majority of Indian ricegrass seedling recruitment. We applied three different densities of white millet (Panicum miliaceum) seeds as “diversionary foods” to plots at three Great Basin study sites in an attempt to reduce rodents' over‐winter cache recovery so that more Indian ricegrass seeds would remain in soil seedbanks and potentially establish new seedlings. One year after diversionary seed application, a moderate level of Indian ricegrass seedling recruitment occurred at two of our study sites in western Nevada, although there was no recruitment at the third site in eastern California. At both Nevada sites, the number of Indian ricegrass seedlings sampled along transects was significantly greater on all plots treated with diversionary seeds than on non‐seeded control plots. However, the density of diversionary seeds applied to plots had a marginally non‐significant effect on seedling recruitment, and it was not correlated with recruitment patterns among plots. Results suggest that application of a diversionary seed type that is preferred by seed‐caching rodents provides a promising passive restoration strategy for target plant species that are dispersed by these rodents.     

Monitoring and modeling the invasion of the fast spreading alien Senecio inaequidens DC. in an alpine region

We modeled the distribution of the South African alien Senecio inaequidens DC. in the Aosta Valley, Western Italian Alps, using data extracted from the Regional floristic database and from an intensive field survey carried out in years 2009–2010. The aims of the work were (1) to evaluate whether the species is in the introduction, colonization, or establishment stage of invasion, (2) to detect the environmental factors that drive the invasion process, and (3) to highlight the potential range of distribution of the alien species. The modeling framework was a stepwise generalized linear model (GLM), using gridded presence/absence data and environmental predictors such as topography, climate, land use, and anthropogenic and natural disturbances. GLM were fit both with and without an additional independent variable to take into account current dispersal limitations. S. inaequidens displayed a very fast spread in the Aosta Valley in the years 1990–2010. The species was positively associated with roads and rivers, southern slopes, and negatively with elevation. However, it was found at an elevation of 1600 m, showing the ability to reach higher elevations than those observed for other invasive alien species, and confirming to be pre-adapted to mountain conditions. The difference between the species distribution models, with and without dispersal constraints, suggested that the availability of seed sources still limits the potential distribution of the species, rather than the environmental variables, and that the realized regional niche differs to a great extent from the equilibrium niche. When limitations to the seed source cease (i.e., in the establishment stage), the species will likely invade large areas that are currently characterized by pastures and grasslands with native species of high agricultural importance. The invasion of S. inaequidens should therefore be considered a serious threat, due to its potential to invade mountain regions, and in particular to colonize habitats used for grazing and forage, thus leading to a high risk for cattle and human health. We discuss the relevance of the results both concerning communication with the public and to support local eradication and control activities. The inclusion of S. inaequidens in the “black list” of the regional law for the conservation of alpine flora (L.R. 45/2009) will help to transfer the information and support invasion control, in particular at medium elevations.     

A large-scale inventory of liana diversity in tropical forests of South Eastern Ghats,India

Among the plant life-forms, lianas, the wood climbers still remain less studied than trees. The forests of Eastern Ghats of India are also relatively under studied compared with the Western Ghats biodiversity hotspot. We conducted a large-scale, landscape-level investigation of liana diversity in six hill complexes of the South Eastern Ghats, which covers 4297 km². We divided the study area into 6.25 km × 6.25 km grids and within each grid a 0.5 ha (5 m × 1000 m) transect was established and all lianas ≥1.5 cm diameter at breast height (dbh) were inventoried in 110 transects totalling a 55-ha area. Liana diversity totalled 143 species in 83 genera and 37 families in the 55 ha sampled. Of these 20 species (28.6%) were endemic to peninsular India and 7 (10%) species belonged to the rare and endangered category. Liana species richness ranged from 8–35 species and density 95–544 individuals per transect. A total of 32 033 liana individuals were enumerated in the 55 ha and the mean abundance was 291 individuals per transect. Across sites, liana abundance varied significantly, but not species richness and basal area. Asclepiadaceae (13 species, 9%) and Apocynaceae (11 species, 8%) constituted the most diverse liana families, followed by Papilionaceae, Vitaceae (10 each, 7%), Convolvulaceae, Mimosaceae, Oleaceae (8 each, 6%), Capparaceae, Rhamnaceae (7 each, 5%) and Menispermaceae (5 species, 3%). In liana stem size distribution, the lowest diameter class (1.5–3 cm dbh) accounted for greatest species richness (137 species, 96%), abundance (27 358 individuals, 85%) and basal area (13.5 m², 36%). The stem twiners were the predominant climber type in terms of species richness (61 species, 42.65%), whereas the armed scramblers were abundant due to stem density (21 571 individuals, 67.34%). The dispersal modes of lianas, assessed by fruit types, revealed zoochory as the prevalent mode (85 species, 59%) indicating the faunal dependence of lianas in the Eastern Ghats landscape. Liana diversity of the Eastern Ghats was compared with inventories made across the tropics. With these baseline data generated on lianas, the importance of biodiversity conservation of the already fragmented South Eastern Ghats region is underlined and potential areas of further research on liana ecology are suggested.     

History of West Mediterranean newts,Pleurodeles (Amphibia: Salamandridae), inferred from old and recent DNA sequences

MtDNA sequences (396 bp cytochrome b and 369 bp 12S rRNA) from recent material and old museum specimens indicate Pleurodeles poireti and P. waltl form independent clades with 7.76% genetic divergence. Within P. poireti, populations from Djebel Edough, NE Algeria are very distinct with 6.12% genetic divergence from the remainder and may deserve separate species status. Away from Djebel Edough, P. poireti consists of three distinct clades (coastal NW Tunisia; central N Algeria; Constantine plus inland NW Tunisia) with a maximum genetic divergence of only 1%. P. waltl contains two clades with 2.96% genetic divergence, one in SE and E Spain plus north Morocco, the other in Portugal and SW and central Spain. Pleurodeles probably invaded NW Africa from SW Europe during the Messinian Salinity Crisis, when land contact was first established at 5.6 Ma, and then interrupted at 5.3 Ma. Molecular clocks, calibrated in the assumption that the latter event separated P. waltl and P. poireti, suggest that Pleurodeles diverged from its sister taxon, Tylototriton, at about 8.6–10 Ma. Djebel Edough P. poireti separated at about 4.2 Ma, perhaps through isolation on a temporary, now ‘fossil’, island initiated by the Messinian crisis. Differentiation in remaining P. poireti may have been caused by Pleistocene climatic fluctuations, while bifurcation in P. waltl appears to have taken place in the Pliocene approximately between 3.2 and 2 Ma. This species reached Morocco very recently, perhaps as a result of human introduction. Use in Pleurodeles of the slower divergence rates estimated in some other salamandrids results in a less parsimonious historical hypothesis that does not fit known geophysical events.     

Forecasting range expansion into ecological traps: climate‐mediated shifts in sea turtle nesting beaches and human development

Some species are adapting to changing environments by expanding their geographic ranges. Understanding whether range shifts will be accompanied by increased exposure to other threats is crucial to predicting when and where new populations could successfully establish. If species overlap to a greater extent with human development under climate change, this could form ecological traps which are attractive to dispersing individuals, but the use of which substantially reduces fitness. Until recently, the core nesting range for the Critically Endangered Kemp's ridley sea turtle (Lepidochelys kempii) was ca. 1000 km of sparsely populated coastline in Tamaulipas, Mexico. Over the past twenty‐five years, this species has expanded its range into populated areas of coastal Florida (>1500 km outside the historical range), where nesting now occurs annually. Suitable Kemp's ridley nesting habitat has persisted for at least 140 000 years in the western Gulf of Mexico, and climate change models predict further nesting range expansion into the eastern Gulf of Mexico and northern Atlantic Ocean. Range expansion is 6–12% more likely to occur along uninhabited stretches of coastline than are current nesting beaches, suggesting that novel nesting areas will not be associated with high levels of anthropogenic disturbance. Although the high breeding‐site fidelity of some migratory species could limit adaptation to climate change, rapid population recovery following effective conservation measures may enhance opportunities for range expansion. Anticipating the interactive effects of past or contemporary conservation measures, climate change, and future human activities will help focus long‐term conservation strategies.     

Simulating the effects of climate change on the distribution of an invasive plant,using a high resolution,local scale,mechanistic approach: challenges and insights

The growing economic and ecological damage associated with biological invasions, which will likely be exacerbated by climate change, necessitates improved projections of invasive spread. Generally, potential changes in species distribution are investigated using climate envelope models; however, the reliability of such models has been questioned and they are not suitable for use at local scales. At this scale, mechanistic models are more appropriate. This paper discusses some key requirements for mechanistic models and utilises a newly developed model (PSS[gt]) that incorporates the influence of habitat type and related features (e.g., roads and rivers), as well as demographic processes and propagule dispersal dynamics, to model climate induced changes in the distribution of an invasive plant (Gunnera tinctoria) at a local scale. A new methodology is introduced, dynamic baseline benchmarking, which distinguishes climate‐induced alterations in species distributions from other potential drivers of change. Using this approach, it was concluded that climate change, based on IPCC and C4i projections, has the potential to increase the spread‐rate and intensity of G. tinctoria invasions. Increases in the number of individuals were primarily due to intensification of invasion in areas already invaded or in areas projected to be invaded in the dynamic baseline scenario. Temperature had the largest influence on changes in plant distributions. Water availability also had a large influence and introduced the most uncertainty in the projections. Additionally, due to the difficulties of parameterising models such as this, the process has been streamlined by utilising methods for estimating unknown variables and selecting only essential parameters.