Genetic Polymorphism and Transplantation Success in the Mediterranean Seagrass Posidonia oceanica

We studied the role of genetic variability of donor beds in establishing transplantation criteria for the Mediterranean seagrass Posidonia oceanica. Horizontal rhizomes, collected from three geographically distinct populations, were transplanted into a common bed at a highly human‐impacted locality. The transplantation site was located near one of the donor populations. After three years, the shoots collected in the population adjacent to the transplanting site showed the lowest growth performance. Genetic variability, assessed through the analysis of hypervariable microsatellite regions, and growth performance followed a similar trend. The shoots growing and branching at the highest rate were those collected from populations with the highest heterozygosity values, despite greater geographic distance. No genetic differences were found between the transplanted shoots and shoots from donor meadows, as expected due to the low rate of sexual reproduction in P. oceanica and the short time that had passed since the transplants. The problem of affecting the local gene pool by the introduction of foreign genotypes could arise, but introduction of new alleles could balance the degradation of genetic variability caused by human impact. In general our study suggests that the genetic variability of source material is an important aspect to consider in the development of seagrass restoration strategies.     

From projected species distribution to food‐web structure under climate change

Climate change is inducing deep modifications in species geographic ranges worldwide. However, the consequences of such changes on community structure are still poorly understood, particularly the impacts on food‐web properties. Here, we propose a new framework, coupling species distribution and trophic models, to predict climate change impacts on food‐web structure across the Mediterranean Sea. Sea surface temperature was used to determine the fish climate niches and their future distributions. Body size was used to infer trophic interactions between fish species. Our projections reveal that 54 fish species of 256 endemic and native species included in our analysis would disappear by 2080–2099 from the Mediterranean continental shelf. The number of feeding links between fish species would decrease on 73.4% of the continental shelf. However, the connectance of the overall fish web would increase on average, from 0.26 to 0.29, mainly due to a differential loss rate of feeding links and species richness. This result masks a systematic decrease in predator generality, estimated here as the number of prey species, from 30.0 to 25.4. Therefore, our study highlights large‐scale impacts of climate change on marine food‐web structure with potential deep consequences on ecosystem functioning. However, these impacts will likely be highly heterogeneous in space, challenging our current understanding of climate change impact on local marine ecosystems.     

Biotic interactions influence the projected distribution of a specialist mammal under climate change

Aim

To measure the effects of including biotic interactions on climate‐based species distribution models (SDMs) used to predict distribution shifts under climate change. We evaluated the performance of distribution models for an endangered marsupial, the northern bettong (Bettongia tropica), comparing models that used only climate variables with models that also took into account biotic interactions.

Location

North‐east Queensland, Australia.

Methods

We developed separate climate‐based distribution models for the northern bettong, its two main resources and a competitor species. We then constructed models for the northern bettong by including climate suitability estimates for the resources and competitor as additional predictor variables to make climate + resource and climate + resource + competition models. We projected these models onto seven future climate scenarios and compared predictions of northern bettong distribution made by these differently structured models, using a ‘global’ metric, the I similarity statistic, to measure overlap in distribution and a ‘local’ metric to identify where predictions differed significantly.

Results

Inclusion of food resource biotic interactions improved model performance. Over moderate climate changes, up to 3.0 °C of warming, the climate‐only model for the northern bettong gave similar predictions of distribution to the more complex models including interactions, with differences only at the margins of predicted distributions. For climate changes beyond 3.0 °C, model predictions diverged significantly. The interactive model predicted less contraction of distribution than the simpler climate‐only model.

Main conclusions

Distribution models that account for interactions with other species, in particular direct resources, improve model predictions in the present‐day climate. For larger climate changes, shifts in distribution of interacting species cause predictions of interactive models to diverge from climate‐only models. Incorporating interactions with other species in SDMs may be needed for long‐term prediction of changes in distribution of species under climate change, particularly for specialized species strongly dependent on a small number of biotic interactions.     

Diel and Seasonal Changes in the Structure of a Decapod (Crustacea: Decapoda) Community of Cymodocea nodosa from Southeastern Spain (West Mediterranean Sea)

The study of a decapod community in a Cymodocea nodosa meadow from Southeastern Spain (Western Mediterranean Sea) showed a stable structure, in which the families Hippolytidae, Processidae, Majidae and Portunidae were the most abundant and the species Hippolyte niezabitowskii dominated. The animal community was more numerous and diverse during the night, showing the existence of nychthemeral movements, which are essentially related to the trophic behaviour and shelter. In this way, many species increased their abundance as a result of an increasing activity and, also, of an influx of other species and specimens from adjacent sandy bottoms, such as Processa spp. (mainly P. modica) Sicyonia carinata, Liocarcinus spp. (mainly juveniles) and several species of hermit crabs, which were rare or absent during the day. All these changes produced modifications in the dominance curves and in the values of all ecological indices (richness, diversity and evenness). Monthly samples were grouped and ordered (MDS) by the factor “day–night”, which showed slight qualitative and quantitative differences (SIMPER, dissimilarity average of the factor day–night = 61.67). On the other hand, no global seasonal differences have been found (one way ANOSIM), but there was a significant level of similarity between winter and spring, while the summer samples were the most different. The differentiation of the summer 1999 can be attributed to a decrease in species abundance and richness, probably due to the dynamics of the decapod populations and the balance with predators (fishes), while that of the summer 2000, to an anomalous event: the massive proliferation of filamentous algae, mainly Ectocarpus s.l., which modified the environmental conditions.     

A genetic assessment of a successful seagrass meadow (Posidonia australis) restoration trial

Seagrass meadows are in decline globally. Although numerous experimental methods have been implemented to restore meadows, few have been successful in the long term. Poor decisions on the sourcing of transplants from donor sites, including poor genetic integration and/or low genetic diversity, may impact on restoration success. However, despite evidence to suggest a positive association between genetic diversity and ecological resilience, there is usually little or no input from genetic data to inform on the genetic management of ecological restoration. Cockburn Sound has seen a 77% decline in seagrass cover since 1967. A transplant trial was conducted between 2004 and 2008 with sprigs of Posidonia australis being planted into a bare sand area. Survival was monitored annually, and in 2012, we compared genetic diversity in this transplant area with the original donor site. Genetic diversity in the restored meadow was very high and comparable to the donor site, with no genetic differentiation detected. The high level of genetic diversity and choice of site may have played an important role in the success of this restoration trial. The observed natural recruits around the site after establishment of transplants suggest that local restoration efforts may improve seafloor habitat and facilitate natural expansion of the meadow.     

Climate‐driven range shifts explain the distribution of extant gene pools and predict future loss of unique lineages in a marine brown alga

The climate‐driven dynamics of species ranges is a critical research question in evolutionary ecology. We ask whether present intraspecific diversity is determined by the imprint of past climate. This is an ongoing debate requiring interdisciplinary examination of population genetic pools and persistence patterns across global ranges. Previously, contrasting inferences and predictions have resulted from distinct genomic coverage and/or geographical information. We aim to describe and explain the causes of geographical contrasts in genetic diversity and their consequences for the future baseline of the global genetic pool, by comparing present geographical distribution of genetic diversity and differentiation with predictive species distribution modelling (SDM) during past extremes, present time and future climate scenarios for a brown alga, Fucus vesiculosus. SDM showed that both atmospheric and oceanic variables shape the global distribution of intertidal species, revealing regions of persistence, extinction and expansion during glacial and postglacial periods. These explained the distribution and structure of present genetic diversity, consisting of differentiated genetic pools with maximal diversity in areas of long‐term persistence. Most of the present species range comprises postglacial expansion zones and, in contrast to highly dispersive marine organisms, expansions involved only local fronts, leaving distinct genetic pools at rear edges. Besides unravelling a complex phylogeographical history and showing congruence between genetic diversity and persistent distribution zones, supporting the hypothesis of niche conservatism, range shifts and loss of unique genetic diversity at the rear edge were predicted for future climate scenarios, impoverishing the global gene pool.     

Consequences of Mediterranean warming events in seagrass (Posidonia oceanica) flowering records

Posidonia oceanica, a seagrass endemic to the Mediterranean forms extended and extremely persistent meadows. It is a clonal plant with an apparently irregular pattern of flowering events. An extensive bibliographic review allowed the reconstruction of past flowering events of this species around the Mediterranean, with a high degree of confidence for the last 30 years. The data series on annual flowering prevalence (FP, flowering records per total records) and flowering intensity (FI, fraction of flowering shoots) produced have been compared with four series on Sea Surface annual Temperature maxima (SST_max) obtained for the NW Mediterranean (averaged from the local data series of l'Estartit and Villefranche: 1957–2005) and for the Eastern, Western basin and the whole Mediterranean sea (extracted from NCEP Reynolds interpolated SST maps: 1982–2005). Significant warming trends are detected in the Mediterranean SST_max series, at a rate of (mean+SE) 0.04±0.01°C yr⁻¹ (R²=0.24, P<0.01, N=24 years), in the Eastern basin series (0.06±0.01°C yr⁻¹, R²=0.43, P<0.001, N=24 years) and in the long SST_max series of the NW Mediterranean (0.02±0.01 C yr⁻¹, R²=0.12, P<0.02, N=49 years). The magnitudes of the SST_max anomalies around the absolute warming trend do not increase with time in any SST_max series. Peaks of FP and FI in the Mediterranean seem to occur each 9–11 years, and coincide with peaks of annual SST_max. Annual FP and FI increase with the residuals of annual SST_max warming trend in all Mediterranean basins (FP_MED: R²=0.27, P<0.01, N=23; FP_NW: R²=0.34, P<0.01, N=31; FP_E: R²=0.20; P<0.10, N=23). An outstanding event of P. oceanica flowering across the Mediterranean has been registered in Autumn 2003; 1 month after the highest annual SST_max recorded in the series. The hypothesis of flowering induction by thermal stress as the possible cause of this relationship is discussed, as well as the potential use of P. oceanica flowering record as early indicator of biological change induced by global sea warming in Mediterranean marine ecosystems.     

Evidence of genomic adaptation to climate in Eucalyptus microcarpa: Implications for adaptive potential to projected climate change

Understanding whether populations can adapt in situ or whether interventions are required is of key importance for biodiversity management under climate change. Landscape genomics is becoming an increasingly important and powerful tool for rapid assessments of climate adaptation, especially in long‐lived species such as trees. We investigated climate adaptation in Eucalyptus microcarpa using the DArTseq genomic approach. A combination of F_ST outlier and environmental association analyses were performed using >4200 genomewide single nucleotide polymorphisms (SNPs) from 26 populations spanning climate gradients in southeastern Australia. Eighty‐one SNPs were identified as putatively adaptive, based on significance in F_ST outlier tests and significant associations with one or more climate variables related to temperature (70/81), aridity (37/81) or precipitation (35/81). Adaptive SNPs were located on all 11 chromosomes, with no particular region associated with individual climate variables. Climate adaptation appeared to be characterized by subtle shifts in allele frequencies, with no consistent fixed differences identified. Based on these associations, we predict adaptation under projected changes in climate will include a suite of shifts in allele frequencies. Whether this can occur sufficiently rapidly through natural selection within populations, or would benefit from assisted gene migration, requires further evaluation. In some populations, the absence or predicted increases to near fixation of particular adaptive alleles hint at potential limits to adaptive capacity. Together, these results reinforce the importance of standing genetic variation at the geographic level for maintaining species’ evolutionary potential.     

Shifts in potential geographical distribution of Pterocarya stenoptera under climate change scenarios in China

Climate change poses a serious threat to biodiversity. Predicting the effects of climate change on the distribution of a species' habitat can help humans address the potential threats which may change the scope and distribution of species. Pterocarya stenoptera is a common fast‐growing tree species often used in the ecological restoration of riverbanks and alpine forests in central and eastern China. Until now, the characteristics of the distribution of this species' habitat are poorly known as are the environmental factors that influence its preferred habitat. In the present study, the Maximum Entropy Modeling (Maxent) algorithm and the Genetic Algorithm for Ruleset Production (GARP) were used to establish the models for the potential distribution of this species by selecting 236 sites with known occurrences and 14 environmental variables. The results indicate that both models have good predictive power. Minimum temperature of coldest month (Bio6), mean temperature of warmest quarter (Bio10), annual precipitation (Bio12), and precipitation of driest month (Bio14) were important environmental variables influencing the prediction of the Maxent model. According to the models, the temperate and subtropical regions of eastern China had high environmental suitability for this species, where the species had been recorded. Under each climate change scenario, climatic suitability of the existing range of this species increased, and its climatic niche expanded geographically to the north and higher elevation. GARP predicted a more conservative expansion. The projected spatial and temporal patterns of P. stenoptera can provide reference for the development of forest management and protection strategies.     

High invasion potential of Hydrilla verticillata in the Americas predicted using ecological niche modeling combined with genetic data

Ecological niche modeling is an effective tool to characterize the spatial distribution of suitable areas for species, and it is especially useful for predicting the potential distribution of invasive species. The widespread submerged plant Hydrilla verticillata (hydrilla) has an obvious phylogeographical pattern: Four genetic lineages occupy distinct regions in native range, and only one lineage invades the Americas. Here, we aimed to evaluate climatic niche conservatism of hydrilla in North America at the intraspecific level and explore its invasion potential in the Americas by comparing climatic niches in a phylogenetic context. Niche shift was found in the invasion process of hydrilla in North America, which is probably mainly attributed to high levels of somatic mutation. Dramatic changes in range expansion in the Americas were predicted in the situation of all four genetic lineages invading the Americas or future climatic changes, especially in South America; this suggests that there is a high invasion potential of hydrilla in the Americas. Our findings provide useful information for the management of hydrilla in the Americas and give an example of exploring intraspecific climatic niche to better understand species invasion.     

Multiple stressors facilitate the spread of a non‐indigenous bivalve in the Mediterranean Sea

Aim

The introduction of non‐indigenous species (NIS) via man‐made corridors connecting previously disparate oceanic regions is increasing globally. However, the environmental and anthropogenic factors facilitating invasion dynamics and their interactions are still largely unknown. This study compiles and inputs available data for the NIS bivalve Brachidontes pharaonis across the invaded biogeographic range in the Mediterranean basin into a species distribution model to predict future spread under a range of marine scenarios.

Location

Mediterranean Sea.

Methods

A systematic review produced the largest presence database ever assembled to inform the selection of biological, chemical and physical factors linked to the spread of B. pharaonis through the Suez Canal. We carried out a sensitivity analysis to simulate current and future trophic and salinity scenarios. A species distribution model was run to determine key drivers of invasion, quantify interactive impacts arising from a range of trophic states, salinity conditions and climatic scenarios and forecast future trajectories for the spread of NIS into new regions under multiple‐parameter scenarios (based on the main factors identified from the systematic review).

Results

Impacts on invasion trajectory arising from climate change and interactions with increasing salinity from the new opening of the canal were the primary drivers of expansion across the basin, the effects of which were further enhanced by eutrophication. Predictions of the current distribution were most accurate when multiple stressors were used to drive the model. A habitat suitability index developed at a subcontinental scale from model outputs identified novel favourable conditions for future colonization at specific locations under 2030 and 2050 climatic scenarios.

Main conclusions

Future expansion of B. pharaonis will be enhanced by climate‐facilitated increased sea temperature, interacting with increasing pressures from salinity and eutrophication. The spatially explicit risk output maps of invasions represent a powerful visual product for use in communication of the spread of NIS and decision‐support tools for scientists and policymakers. The suggested approach, the observed distribution pattern and driving processes can be applied to other NIS species and regions by providing novel forecasts of species occurrences under future multiple stressor scenarios and the location of suitable recipient habitats with respect to anthropogenic and environmental parameters.     

Ecophysiological constraints shape autumn migratory response to climate change in the North American field sparrow

Our ability to accurately forecast species' geographical responses to climate change requires knowledge of the proximate and ultimate drivers of their distribution. Here, we consider the ecophysiological and demographic determinants of the distribution of a partial migrant, the North American field sparrow, Spizella pusilla. From 1940 to 1963, the field sparrow extended its winter northern range margin 222km polewards. Such expansion was coincident with not only a geographical expansion into suitable breeding habitats, but also a decrease in mean abundance across sites occupied during the winter surveys. Combined, these trends suggest that declining populations along the expansion front either stopped migrating or altered their autumn migration. The poleward expansion was not coincident with climatically induced decreases in peak metabolic energy demand, but it did track increases in ecosystem net primary productivity. After 1963, the species' lower lethal temperature prevented further poleward movement. These findings show how different ecophysiological constraints can interact to change migration and distribution in a demographically declining species.