Vulnerability to xylem embolism as a major correlate of the environmental distribution of rain forest species on a tropical island

Increases in drought‐induced tree mortality are being observed in tropical rain forests worldwide and are also likely to affect the geographical distribution of tropical vegetation. However, the mechanisms underlying the drought vulnerability and environmental distribution of tropical species have been little studied. We measured vulnerability to xylem embolism (P₅₀) of 13 woody species endemic to New Caledonia and with different xylem conduit morphologies. We examined the relation between P₅₀, along with other leaf and xylem functional traits, and a range of habitat variables. Selected species had P₅₀ values ranging between ?4.03 and ?2.00 MPa with most species falling in a narrow range of resistance to embolism above ?2.7 MPa. Embolism vulnerability was significantly correlated with elevation, mean annual temperature and percentage of species occurrences located in rain forest habitats. Xylem conduit type did not explain variation in P₅₀. Commonly used functional traits such as wood density and leaf traits were not related to embolism vulnerability. Xylem embolism vulnerability stands out among other commonly used functional traits as a major driver of species environmental distribution. Drought‐induced xylem embolism vulnerability behaves as a physiological trait closely associated with the habitat occupation of rain forest woody species.     

Genetic variation of Mimetes hirtus and Mimetes fimbriifolius (Proteaceae) – a comparative analysis of two closely related fynbos species

We investigated the influence of differing life history traits on the genetic structure of the related species Mimetes fimbriifolius and Mimetes hirtus (Proteaceae), which occur in the South African fynbos. Both species are bird‐pollinated and ant‐dispersed, but differ in rarity, longevity, ecological strategy and the fragmentation of their distribution area. We used AFLPs to study genetic variation within and between 21 populations of these two species across their distribution range. AFLP analysis revealed significantly higher genetic variation within populations of M. fimbriifolius than within M. hirtus. While M. fimbriifolius clearly lacked any significant genetic differentiation between populations, a distinct geographic pattern was observed for M. hirtus. Differentiation was, however, stronger at the regional (Φ_PT = 0.57) than at the local scale (Φ_PT = 0.08). Our results clearly indicate that even closely related species that share the same mode of pollination and seed dispersal can differ in their genetic structure, depending on the magnitude of fragmentation, longevity of individuals and ecological strategy.     

The vulnerability of species to range expansions by predators can be predicted using historical species associations and body size

Climate change threatens species directly through environmental changes and indirectly through its effects on species interactions. We need tools to predict which species are most vulnerable to these threats. Pairwise species associations and body size are simple but promising predictors of the relative impact of species introduced outside of their historical ranges. We examined the vulnerability of 30 fish species to the impacts of three centrarchid predators that are being introduced to lakes north of their historical range boundaries. Species that were negatively associated with each centrarchid in their historical range were more likely to be lost from lakes with centrarchid introductions. Total body length was most important in predicting impact for the most gape-limited predator. At the regional scale, our method identifies those species most vulnerable to introductions facilitated by climate change and can easily be applied to a range of taxa undergoing range expansions.     

Effects of temperature on life histories of three endangered Japanese diving beetle species

To elucidate population-increasing factors in the diving beetle Cybister tripunctatus lateralis (Fabricius) (Coleoptera: Dytiscidae) in Japan in recent years, life histories and oviposition patterns were compared among three endangered diving beetle species, Cybister brevis Aubé (qualified by the Japanese Red Data List as ‘near threatened’), Cybister chinensis Motschulsky (vulnerable), and C. tripunctatus lateralis (vulnerable). Oviposition in C. brevis, C. chinensis, and C. tripunctatus lateralis was observed from late April to mid-June, from late April to early July, and from late May to mid-August, respectively, under semi-outdoor conditions. There were no interspecies differences in total hatchling production during the reproductive season. In rearing experiments at various temperatures (20, 23, 25, 28, and 30 °C), the mortality of C. tripunctatus lateralis larvae was higher at 20 °C, and gradually lower with increasing temperature up to 30 °C. Adult body size of females in C. tripunctatus lateralis is larger than that of males but there were no significant differences among temperatures (25–30 °C). Cybister brevis had a higher emergence rate at 23–28 °C than at 20 and 30 °C. In C. brevis, the body size of adults reared at 25 or 28 °C was significantly larger than at other temperatures. Cybister chinensis did not differ in emergence rate and adult body size among the five temperature conditions. The developmental zero (i.e., the lower developmental threshold) from the first instar to adult emergence was 11.1 °C for C. brevis, 8.7 °C for C. chinensis, and 16.8 °C for C. tripunctatus lateralis. We speculate how the influence of global warming may have a positive impact on the growth and survival of C. tripunctatus lateralis.     

Body size‐dependent responses of a marine fish assemblage to climate change and fishing over a century‐long scale

Commercial fishing and climate change have influenced the composition of marine fish assemblages worldwide, but we require a better understanding of their relative influence on long‐term changes in species abundance and body‐size distributions. In this study, we investigated long‐term (1911–2007) variability within a demersal fish assemblage in the western English Channel. The region has been subject to commercial fisheries throughout most of the past century, and has undergone interannual changes in sea temperature of over 2.0 °C. We focussed on a core 30 species that comprised 99% of total individuals sampled in the assemblage. Analyses showed that temporal trends in the abundance of smaller multispecies size classes followed thermal regime changes, but that there were persistent declines in abundance of larger size classes. Consistent with these results, larger‐growing individual species had the greatest declines in body size, and the most constant declines in abundance, while abundance changes of smaller‐growing species were more closely linked to preceding sea temperatures. Together these analyses are suggestive of dichotomous size‐dependent responses of species to long‐term climate change and commercial fishing over a century scale. Small species had rapid responses to the prevailing thermal environment, suggesting their life history traits predisposed populations to respond quickly to changing climates. Larger species declined in abundance and size, reflecting expectations from sustained size‐selective overharvesting. These results demonstrate the importance of considering species traits when developing indicators of human and climatic impacts on marine fauna.     

Phylogeny, biogeography, and the evolution of life-history traits in Leucadendron (Proteaceae)

Leucadendron is a moderately large genus of Proteaceae almost entirely restricted to the Cape Floristic Region of southern Africa. The genus is unusual in being dioecious and sexually dimorphic. ITS sequence data were obtained from 62 of the 96 currently recognized taxa (85 species and 11 subspecies). Phylogenetic analyses were conducted under Maximum Likelihood and parsimony and resolved nine groups of species with varying degrees of bootstrap support, but relationships between these groups are largely unsupported. The phylogeny conflicts with the current taxonomic arrangement, which is based mainly on fruit morphology. The two sections of the genus, Alatosperma and Leucadendron, and several subsections within these sections, are resolved as non-monophyletic. This means that taxonomically important characters (such as fruit shape) have evolved multiple times, as the species with nut-like fruit (resolved into two of the nine groups) appear to have evolved independently from ancestors with winged fruit. Based on the topology obtained, the life history traits of anemophily, myrmechochory, and re-sprouting have also originated multiple times. Dispersal-Vicariance (DIVA) analysis suggests that the genus had an ancestral area in the Karoo Mountain and Southeastern phytogeographic centres of endemism in the southwestern Cape.     

Current temporal trends in moth abundance are counter to predicted effects of climate change in an assemblage of subarctic forest moths

Changes in climate are influencing the distribution and abundance of the world's biota, with significant consequences for biological diversity and ecosystem processes. Recent work has raised concern that populations of moths and butterflies (Lepidoptera) may be particularly susceptible to population declines under environmental change. Moreover, effects of climate change may be especially pronounced in high latitude ecosystems. Here, we examine population dynamics in an assemblage of subarctic forest moths in Finnish Lapland to assess current trajectories of population change. Moth counts were made continuously over a period of 32 years using light traps. From 456 species recorded, 80 were sufficiently abundant for detailed analyses of their population dynamics. Climate records indicated rapid increases in temperature and winter precipitation at our study site during the sampling period. However, 90% of moth populations were stable (57%) or increasing (33%) over the same period of study. Nonetheless, current population trends do not appear to reflect positive responses to climate change. Rather, time‐series models illustrated that the per capita rates of change of moth species were more frequently associated negatively than positively with climate change variables, even as their populations were increasing. For example, the per capita rates of change of 35% of microlepidoptera were associated negatively with climate change variables. Moth life‐history traits were not generally strong predictors of current population change or associations with climate change variables. However, 60% of moth species that fed as larvae on resources other than living vascular plants (e.g. litter, lichen, mosses) were associated negatively with climate change variables in time‐series models, suggesting that such species may be particularly vulnerable to climate change. Overall, populations of subarctic forest moths in Finland are performing better than expected, and their populations appear buffered at present from potential deleterious effects of climate change by other ecological forces.     

Functional leaf and size traits determine the photosynthetic response of 10 dryland species to warming

Aims Relatively few studies so far have assessed how ongoing global warming will affect the photosynthetic performance of dryland plant species. We evaluated the effects of warming on the photosynthetic rates of 10 species with contrasting functional attributes, and whether their functional traits modulated photosynthetic responses to warming.Methods A common garden experiment was conducted over 2 years with distinct environmental conditions (drier vs. wetter year). The experiment was designed as a randomized block design with two treatments: warming (control vs. ~2.9°C temperature increase) and species (Agropyron cristatum, Festuca ovina, Lygeum spartum, Medicago sativa, Plantago lanceolata, Psoralea bituminosa, Sanguisorba minor, Hedysarum coronarium, Dorycnium pentaphyllum and Phlomis herba-venti). We linked functional traits measurements with temporal variations in photosynthetic responses to warming.Important findings In the drier year, warming increased photosynthetic rates at the beginning of the growing season, suggesting a modification in the growing period (earlier spring). In the wetter year, functional traits modulated photosynthetic responses to warming. Larger species with shorter leaves (e.g. M. sativa) had higher photosynthetic rates under warming compared to smaller species with larger leaves (e.g. F. ovina). Our results highlight the importance of (i) studying photosynthetic responses along different years and (ii) considering functional traits when evaluating photosynthetic responses to climate change, particularly in stressful environments such as drylands.     

Genetic structure and life history are key factors in species distribution models of spiny lobsters

AimWe incorporated genetic structure and life history phase in species distribution models (SDMs) constructed for a widespread spiny lobster, to reveal local adaptations specific to individual subspecies and predict future range shifts under the RCP 8.5 climate change scenario.LocationIndo‐West Pacific.MethodsMaxEnt was used to construct present‐day SDMs for the spiny lobster Panulirus homarus and individually for the three genetically distinct subspecies of which it comprises. SDMs incorporated both sea surface and benthic (seafloor) climate layers to recreate discrete influences of these habitats during the drifting larval and benthic juvenile and adult life history phases. Principle component analysis (PCA) was used to infer environmental variables to which individual subspecies were adapted. SDM projections of present‐day habitat suitability were compared with predictions for the year 2,100, under the RCP 8.5 climate change scenario.ResultsIn the PCA, salinity best explained P. h. megasculptus habitat suitability, compared with current velocity in P. h. rubellus and sea surface temperature in P. h. homarus. Drifting and benthic life history phases were adapted to different combinations of sea surface and benthic environmental variables considered. Highly suitable habitats for benthic phases were spatially enveloped within more extensive sea surface habitats suitable for drifting larvae. SDMs predicted that present‐day highly suitable habitats for P. homarus will decrease by the year 2,100.Main conclusionsIncorporating genetic structure in SDMs showed that individual spiny lobster subspecies had unique adaptations, which could not be resolved in species‐level models. The use of sea surface and benthic climate layers revealed the relative importance of environmental variables during drifting and benthic life history phases. SDMs that included genetic structure and life history were more informative in predictive models of climate change effects.     

The ecology of saprophagous macroarthropods (millipedes,woodlice) in the context of global change

Millipedes (Diplopoda) and woodlice (Crustacea, Isopoda), with a total of about 15000 described species worldwide, contribute substantially to invertebrate biodiversity. These saprophagous macroarthropods, which are key regulators of plant litter decomposition, play an important role in the functioning of terrestrial ecosystems in tropical and temperate areas. Herein we review current knowledge on the effects of climate, food quality and land cover on millipede and woodlouse species to explore their potential responses to global change. Essentially similar trends are observed in the two taxa. Experiments have shown that climate warming could result in higher rates of population growth and have positive effects on the abundance of some temperate species. This is consistent with signs of northward expansion in Europe, although the mechanisms of dispersal remain unclear. The generality of this finding is evaluated in relation to the life histories and geographical distributions of species. At low latitudes, interactions with more severe droughts are likely and could affect community composition. Elevated atmospheric CO₂ levels and changes in plant community composition are expected to alter leaf litter quality, a major determinant of macroarthropod fertility via the link with female adult body size. Although food quality changes have been shown to influence population growth rates significantly, it is proposed that the effects of warming will be probably more important during the coming decades. Land cover changes, mainly due to deforestation in the tropics and land abandonment in Europe, are critical to habitat specialists and could override any other effect of global change. Habitat destruction by man may be the main threat to macroarthropod species, many of which are narrow endemics. At the landscape scale, habitat heterogeneity could be a good option for conservation, even at the cost of some fragmentation. Two principal areas are identified which require further work: (i) the effects of climate change across broader geographic ranges, and on species with different ecologies and life histories; (ii) the effects of global change on both macroarthropods and their natural enemies (predators, parasites and pathogens), to improve predictions in field situations.     

Diverse migratory histories of Japanese Trachidermus and Cottus species (Cottidae) as inferred from otolith microchemistry

The migratory histories of Japanese freshwater sculpins, one Trachidermus and four Cottus species, were studied by examining strontium (Sr) and calcium (Ca) concentrations in their otoliths using wavelength dispersive X‐ray spectrometry on an electron microprobe. The Sr : Ca ratios in the otoliths changed with salinity of the habitat. The otoliths of Cottus nozawae showed consistently low Sr : Ca ratios, with an average of 3·37 × 10^?3 from the core to the edge, suggesting a freshwater resident life cycle. In contrast, the otolith Sr : Ca ratios for Trachidermus fasciatus and Cottus kazika changed along the life history transects possibly in accordance with their migration patterns from sea to fresh water. The ratios of T. fasciatus and C. kazika averaged 5·4 × 10^?3 and 5·3 × 10^?3 respectively, in the otolith region from the core to the points 450–890 μm, and changed to the lower levels, averaging 2·0 × 10^?3 and 2·7 × 10^?3, in the outer otolith region. These data suggest that both the species have a catadromous life cycle. The otoliths of Cottus hangiongensis had low Sr : Ca ratios in the two regions from the core to the points 15–30 μm and the points 415–582 μm to the edge, averaging 2·0 × 10^?3 and 1·9 × 10^?3, with significantly higher ratios in the narrow area between these regions, averaging 4·6 × 10^?3. Similar ontogenetic changes in otolith Sr : Ca ratios were found in the otoliths of Cottus amblystomopsis, suggesting their amphidromous life cycle. These findings suggest that otolith Sr : Ca ratios reflect individual life histories and that Japanese Trachidermus and Cottus species have diverse migratory histories.     

Historic range dynamics in Kaiser's mountain newt (Neurergus kaiseri): Insights from phylogeographic analyses and species distribution modeling

Vulnerable Kaiser''s mountain newt, Neurergus kaiseri, is endemic to highland streams, springs, and pools of the southwestern Zagros mountain, Iran. The present study aimed to use an integration of phylogeographical and species distribution modeling (SDM) approaches to provide new insights into the evolutionary history of the species throughout Quaternary climate oscillations. The phylogeographical analysis was followed by analyzing two mitochondrial DNA (mt‐DNA) markers including 127 control region (D‐loop) and 72 NADH dehydrogenase 2 (ND2) sequences from 15 populations in the entire species range that were obtained from GenBank. Potential recent and past distribution (the Last Glacial Maximum, LGM, 21 Kya and the Mid‐Holocene, 6 Kya) reconstructed by ensemble SDM using nine algorithms with CCSM4, MIROC‐ESM, and MPI‐ESM‐P models. N. kaiseri displayed two distinct lineages in the northern and southern regions that diverged in the Early‐Pleistocene. The demographics analysis showed signs of a slight increase in effective population size for both northern and southern populations in the Mid‐Pleistocene. Biogeography analysis showed that both vicariance and dispersal events played an important role in the formation of recent species distribution of N. kaiseri. Based on SDM projection onto paleoclimatic data, N. kaiseri displayed a scenario of past range expansion that followed by postglacial contraction. The models showed that the distribution range of the species may have shifted to a lower altitude during LGM while with amelioration of climatic during Mid‐Holocene to recent conditions caused the species to shift to the higher altitude. The findings of the current study support the hypothesis that the Zagros mountains​ may be acting as climatic refugia and play an important role in the protection of isolated populations during climate oscillations.     

Millipedes faced with drought: the life cycle of a Mediterranean population of Ommatoiulus sabulosus (Linnaeus) (Diplopoda,Julida, Julidae)

Growth, development and life-cycle duration of the millipede Ommatoiulussabulosus (f.aimatopodus) were studied in a Mediterranean shrubland of southern France and compared with previous data from northwest Europe. Changes in the proportions of stadia during the course of the year were analysed in several generations. The results show that stadia VII and VIII are consistently reached after the first year of growth, and stadia IX and X after the second year. First reproduction may occur at the age of two years in males reaching maturity at stadium X, but not until the age of three in those reaching maturity at stadia XI and XII. Reproduction cannot occur until at least the age of three in females, which carry mature eggs from stadium XI onwards. In comparison with more northern populations, life-cycle duration is not shorter in the Mediterranean population but there are marked differences in its phenology: the breeding period is in autumn, so that juveniles of stadia II to VI are never faced with the summer drought, and larger individuals are mostly inactive in summer; moreover, all individuals moult once every winter. The results illustrate how julid millipedes of humid temperate regions could respond to higher temperatures and drier summer conditions in the context of climate change.     

Chasing a changing climate: Reproductive and dispersal traits predict how sessile species respond to global warming

Aim

Studies of species' range shifts have become increasingly relevant for understanding ecology and biogeography in the face of accelerated global change. The combination of limited mobility and imperilled status places some species at a potentially greater risk of range loss, extirpation or extinction due to climate change. To assess the ability of organisms with limited movement and dispersal capabilities to track shifts associated with climate change, we evaluated reproductive and dispersal traits of freshwater mussels (Unionida), sessile invertebrates that require species‐specific fish for larval dispersal.

Location

North American Atlantic Slope rivers.

Methods

To understand how unionid mussels may cope with and adapt to current and future warming trends, we identified mechanisms that facilitated their colonization of the northern Atlantic Slope river basins in North America after the Last Glacial Maximum. We compiled species occurrence and life history trait information for each of 55 species, and then selected life history traits for which ample data were available (larval brooding duration, host fish specificity, host infection strategy, and body size) and analysed whether the trait state for each was related to mussel distribution in Atlantic Slope rivers.

Results

Brooding duration (p < .01) and host fish specificity (p = .02) were significantly related to mussel species distribution. Long‐term brooders were more likely than short‐term brooders to colonize formerly glaciated rivers, as were host generalists compared to specialists. Body size and host infection strategy were not predictive of movement into formerly glaciated rivers (p > .10).

Main conclusions

Our results are potentially applicable to many species for which life history traits have not been well‐documented, because reproductive and dispersal traits in unionid mussels typically follow phylogenetic relationships. These findings may help resource managers prioritize species according to climate change vulnerability and predict which species might become further imperilled with climate warming. Finally, we suggest that similar trait‐based decision support frameworks may be applicable for other movement limited taxa.

     

Differences among six woody perennials native to Northern Europe in their level of genetic differentiation and adaptive potential at fine local scale

The ability of perennial species to adapt their phenology to present and future temperature conditions is important for their ability to retain high fitness compared to other competing plant species, pests, and pathogens. Many transplanting studies with forest tree species have previously reported substantial genetic differentiation among populations within their native range. However, the question of “how local is local” is still highly debated in conservation biology because studies on genetic patterns of variation within and among populations at the local scale are limited and scattered. In this study, we compare the level of genetic differentiation among populations of six different perennial plant species based on their variation in spring flushing. We assess the level of additive genetic variation present within the local population. For all six species, we find significant differentiation among populations from sites with mean annual temperature ranging between 7.4°C and 8.4°C. The observed variation can only be partly explained by the climate at the site of origin. Most clear relationship between early flushing and higher average spring temperature is observed for the three wind‐pollinated species in the study, while the relations are much less clear for the three insect‐pollinated species. This supports that pollination system can influence the balance between genetic drift and natural selection and thereby influence the level of local adaptation in long‐lived species. On the positive side, we find that the native populations of woody plant species have maintained high levels of additive genetic variation in spring phenology, although this also differs substantially among the six studied species.     

Resistance to complete submergence in Rumex species with different life histories: the influence of plant size and light

Resistance to complete submergence was tested in three Rumex species that occur in the Dutch river forelands. The species differ in both habitat and life history characteristics. The annual or biennial R. maritimus and the biennial or short lived perennial R. palustris grow on frequently flooded mud flats of low elevation, while the perennial R. thyrsiflorus can be found on dykes and river dunes that are seldom flooded. The flooding characteristics of the habitats of the three species were determined. These data were used to design experiments to determine the survival and biomass development of the three species during submergence and the influence of plant size and light level on these parameters. It was shown in all three species that plants submerged during daytime were much more resistant to flooding than those submerged at night. This is most probably due to the generation of oxygen or carbohydrates by underwater photosynthesis. Mature plants of the three species showed higher survival after submergence than juvenile plants, which might be caused by higher carbohydrate levels in the taproots of mature plants. In addition, the three species clearly differed in survival and biomass development during submergence. Rumex thyrsiflorus , the species least subjected to flooding, is least tolerant to complete submergence. Rumex maritimus , which can avoid the floods by having a short life cycle, is less tolerant to submergence than R. palustris , which has to survive the floods as a vegetative plant. It was noted that some plants that survived the flooding period itself, still died in the following period of drained conditions, possibly due to post-anoxic injury.     

Growth responses to waterlogging and drainage of woody Hakea (Proteaceae) seedlings,originating from contrasting habitats in south-western Australia

We investigated the responses of seven woody Hakea (Proteaceae) species (two populations of each), to two months of waterlogging and subsequent drainage, in a controlled glasshouse experiment. The species originated from contrasting environments (winter-wetland versus non-wetland habitats), and differed in abundance (endangered ironstone species versus common species). Waterlogging arrested growth of the main root system, and stimulated the formation of superficial adventitious roots just below the root/shoot junction in all species. Wetland species produced at least twice the amount of adventitious root dry mass of that of non-wetland species, due to differences in number, length or degree of branching. Their adventitious roots also tended to have higher porosities (7–10% versus 5–6% gas spaces). The relative amount of adventitious roots formed was strongly, positively correlated with the maintenance of shoot growth, and only the non-wetland species showed significant shoot growth reductions (19%) upon waterlogging. Dry mass percentage of stems and leaves, and leaf dry mass per area (LMA) increased considerably during waterlogging in all species (averages of 15, 29 and 27%, respectively), returning to the values of continuously drained control plants after drainage. Similarly, upon drainage, a suppression of shoot growth (average 35%) and a stimulation of root growth (average 50%) restored the root mass ratios to those of control plants. We found a negative correlation between the maintenance of growth during waterlogging versus that after waterlogging, suggesting a trade-off in functioning of the superficial adventitious roots between waterlogged and drained conditions. The rare winter-wet ironstone endemics resembled the common winter-wet species in most of their responses to waterlogging and drainage. Therefore, the results presented here cannot offer an explanation for their different distribution patterns. Our results suggest that non-wetland species may be disadvantaged in a wetland environment, due to their lower capacity to form adventitious roots resulting in stronger growth reductions.