Aim: To test two prominent, alternate hypotheses that provide explanations for the great accumulation of endemic species in the Kimberley bioregion in north-western Australia, using an extensively sampled, region wide phylogeny of northern Australia’s most speciose freshwater fish family, Terapontidae. Specifically, we test whether the Kimberley may act as (1) a “museum” accumulating taxa and endemic species over time or (2) a “cradle” of more recent diversification and neoendemism. Location: The Australian monsoonal tropics
Taxon: Grunters (Terapontidae) Methods: We obtained a robust and well supported Bayesian phylogeny for the family using DNA sequences from mtDNA and nuclear gene regions. We performed molecular phylogenetic analyses using species tree methods including molecular dating analysis, ancestral range reconstruction, and diversification analysis. Results: Based on our phylogeny, the combined molecular clock estimates and likelihood-based historical biogeographic reconstructions suggest that terapontids recently transitioned into the Kimberley from the east during the late-Miocene. We found that 80% of Kimberley terapontids diversified within the Kimberley in the last 3 Ma. Further, diversification analyses identified a single significant shift in diversification rates ~1.4 Ma that corresponds with a change in global climate midway through the Pleistocene that was predominantly driven by speciation in the Kimberley. Main Conclusions: The weight of evidence suggests that the Kimberley has been a “cradle” of evolution for Terapontidae, rather than a “museum”. Our analysis provides strong evidence for a geologically recent transition of terapontids into the Kimberley from regions to the east during the late Miocene followed by a significant increase in speciation rates during the Pleistocene, driven by speciation in the Kimberley. The results provide important insight into the evolutionary and biogeographical processes that have shaped the regions unique biota, which will inform land managers working to protect and conserve both species and the processes responsible for generating and sustaining them.
Contributors:Harris R.L., Nicol S.C., Morrow G.E.
1. Echidnas are egg-laying mammals found across Australia and in Tasmania they hibernate resulting in a most unusual mating system: males enter hibernation in late summer-early autumn and arouse in late autumn-early winter to mate, although females are still hibernating. Groups of males compete for matings and both males and females mate with multiple partners. Females that mate early return to hibernation even when pregnant, and males continue to mate with pregnant females. We asked to what extent to can the bizarre combination of behavioural and physiological features that characterize reproduction of Tasmanian echidnas be attributed to their phylogeny, and how much is a consequence of their ecology? 2. To understand the interaction between energetics and the echidna mating system in determining the timing of echidna hibernation we analysed data from an 18-year study of a wild population of Tasmanian echidnas 3. Males with high fat reserves arouse earliest and seek out suitable females, and females that mate early in the mating season re-enter hibernation while pregnant. 4. Competition between males drives early mating and while mating with males in the best condition could be advantageous for females and their young, egg-laying in winter is potentially disadvantageous, and post-mating hibernation by females is a means of delaying hatching of young until environmental conditions are more favourable. This post-mating hibernation by females is usually disrupted by males which mate with them although they are already pregnant.
5. Comparisons with other echidna populations suggests that a decreased activity period due to hibernation has not increased male-male competition. 6. Similar competition between groups of males for access to females is seen in chlamyphorid armadillos, which occupy a similar ecological niche to echidnas.
1. Responding to the information provided by others is an important foraging strategy in many species. Through social foraging, individuals can more efficiently find unpredictable resources and thereby increase their foraging success. 2. When individuals are more socially responsive to particular phenotypes than others, however, the advantage they obtain from foraging socially is likely to depend on the phenotype composition of the social environment. We tested this hypothesis by performing experimental manipulations of guppy, Poecilia reticulata, sex compositions in the wild. 3. Males found fewer novel food patches in the absence of females than in mixed-sex compositions, while female patch discovery did not differ regardless of the presence or absence of males. 4. We argue that these results were driven by sex-dependent mechanisms of social association: Markov chain-based fission-fusion modelling revealed that less social individuals found fewer patches and that males reduced sociality when females were absent. In contrast, females were similarly social with or without males. 5. Our findings highlight the relevance of considering how individual and population-level traits interact in shaping the advantages of social foraging in the wild.
Contributors:Little, Chelsea Jean, Fronhofer, Emanuel A., Altermatt, Florian
A major focus of ecology is to understand and predict ecosystem function across scales. Many ecosystem functions are only measured at local scales, while their effects occur at a landscape level. Here, we investigate how landscape-scale predictions of ecosystem function depend on intraspecific competition, a fine-scale process, by manipulating intraspecific density of shredding macroinvertebrates and examining effects on leaf litter decomposition, a key function in freshwater ecosystems. For two species, we found that per-capita leaf processing rates declined with increasing density following power functions with negative exponents, likely due to interference competition. To demonstrate consequences of this nonlinearity, we scaled up estimates of leaf litter processing from shredder abundance surveys in 10 replicated headwater streams. In accordance with Jensen’s inequality, applying density-dependent consumption rates reduced estimates of catchment-scale leaf consumption by an order of magnitude relative to density-independent rates. Density-dependent consumption estimates aligned closely with metabolic requirements in catchments with large, but not small, shredder populations. Importantly, shredder abundance was not limited by leaf litter availability and catchment-level leaf litter supply was much higher than estimated consumption. Thus leaf litter processing was not limited by resource supply. Our work highlights the need for scaling-up which accounts for intraspecific interactions.
Contributors:Nicolas E., Maestre F.T., Nortes P., Prieto I., Querejeta J.I., Leon-Sanchez L.
Climate change will increase heat and drought stress in many dryland areas, which could reduce soil nutrient availability for plants and aggravate nutrient limitation of primary productivity. Any negative impacts of climate change on foliar nutrient contents would be expected to negatively affect the photosynthetic capacity, water use efficiency and overall fitness of dryland vegetation.
We conducted a four-year manipulative experiment using open top chambers and rainout shelters to assess the impacts of warming (~2ºC, W), rainfall reduction (~30%, RR) and their combination (W+RR) on the nutrient status and ecophysiological performance of six native shrub species of contrasting phylogeny in a semiarid ecosystem. Leaf nutrient status and gas exchange were assessed yearly, whereas biomass production and survival were measured at the end of the study.
Warming (W and W+RR) advanced shoot growth phenology and reduced foliar macro- (N, P, K) and micronutrient (Cu, Fe, Zn) concentrations (by 8-18% and 14-56%, respectively), net photosynthetic rate (32%), aboveground biomass production (28-39%) and survival (23-46%). Decreased photosynthesis and growth in W and W+RR plants was primarily linked to enhanced nutritional constraints on carbon fixation. Poor leaf nutrient status in W and W+RR plants partly decoupled carbon assimilation from water flux and led to drastic reductions in water use efficiency (WUEi; ~41%) across species. The RR treatment moderately decreased foliar macro- and micronutrients (6-17%, except for Zn) and biomass production (22%). The interactive impacts of warming and rainfall reduction (W+RR treatment) on plant performance were generally smaller than expected from additive single‐factor effects.
Synthesis: Large decreases in plant nutrient pool size and productivity combined with increased mortality during hotter droughts will reduce vegetation cover and nutrient retention capacity, thereby disrupting biogeochemical processes and accelerating dryland degradation with impending climate change. Increased macro- and micronutrient co-limitation of photosynthesis with forecasted climate change conditions may offset any gains in WUEi and productivity derived from anthropogenic CO2 elevation, thereby increasing dryland vegetation vulnerability to drought stress in a warmer and drier climate. The generalized reduction in leaf nutrient contents with warming compromises plant nutritional quality for herbivores, with potential cascading negative effects across trophic levels.
Contributors:Borges R.M., Gupta S.
1. Mutualisms are often subject to perturbations by parasitism arising from third-party interactions. How third-party perturbations are dampened is a fundamental question pertaining to mutualism stability. Phoretic organisms that turn parasitic within a mutualism may destabilise it. If the fitness cost of such phoresy is high, then density-dependent effects could be one mechanism to stabilize these interactions.
2. We experimentally examined the fitness effects of a phoretic nematode community on a brood-site pollination mutualism involving a pollinating fig wasp (the vehicle) and its associated fig species (the host for wasp and nematode development).
3. We comprehensively investigated fitness impacts of phoresy on wasp lifespan, lifetime reproductive success, dispersal ability and predation risk as well as on host brood-site volume and seed number. We employed a range of hitchhiker densities that encompassed natural and overloading levels for two nematode taxa (one plant- and one animal-parasitic type).
4. None of the plant host and vehicle fitness parameters were affected by wasps with low nematode transportation loads for either type of nematode. Furthermore, wasps arriving at their destinations carried lower densities of both animal- and plant-parasitic nematodes compared to dispersing wasps suggesting that there is selection on hitchhiker numbers during the dispersal process, and that wasps loaded with a greater density of nematodes do not successfully disperse. Overloaded wasps had shorter flight durations, suggesting limited dispersal ability; on arrival at their destination they suffered greater predation risk. Such overloaded wasps delivered impaired pollination services and produced fewer offspring resulting in lower lifetime fitness. Therefore, the direct and indirect effects of nematodes on their vehicles are strong. These effects also translated into impacts on host plant fitness, with the overloaded pollinators promoting the development of smaller brood-sites with fewer seeds, thus reducing fig tree reproductive success. The effects of the animal parasites were greater than that of the plant parasite in this study.
5. The third-party interaction is therefore self-limited and exhibits density dependence. The strong negative effects of overloading likely explain the low number of nematodes found in nature on dispersing and arriving fig wasps. Consequently, parasitic hitchhikers do not destabilise the mutualism.
Tropical forests, a key-category of land ecosystems, are faced with the world’s highest levels of habitat conversion and associated biodiversity loss. In tropical Asia, Dipterocarpaceae are one of the economically and ecologically most important tree families, but their genomic diversity and evolution remain understudied, hampered by a lack of available genetic resources. Southern China represents the northern limit for Dipterocarpaceae, and thus changes in habitat ecology, community composition and adaptability to climatic conditions are of particular interest in this group. Phylogenomics is a tool for exploring both biodiversity and evolutionary relationships through space and time using plastome, nuclear and mitochondrial genome. We generated full plastome and Nuclear Ribosomal Cistron (NRC) data for Chinese Dipterocarpaceae species as a first step to improve our understanding of their ecology and evolutionary relationships. We generated the plastome of Dipterocarpus turbinatus, the species with the widest distribution using it as a baseline for comparisons with other taxa. Results showed low level of genomic diversity among analysed range-edge species, and different evolutionary history of the incongruent NRC and plastome data. Genomic resources provided in this study will serve as a starting point for future studies on conservation and sustainable use of these dominant forest taxa, phylogenomics and evolutionary studies.
Contributors:Withler R.E., Lynch C., Beacham T.D., Jonsen K., McIntosh B., Wallace C., Willis D., Candy J.R.
In salmonid parentage-based tagging (PBT) applications, entire hatchery broodstocks are genotyped, and subsequently progeny can be non-lethally sampled and assigned back to their parents using parentage analysis, thus identifying their hatchery of origin and brood year (i.e. age). Inter- and intra-population variability in migration patterns, life history traits, and fishery contributions can be determined from PBT analysis of samples derived from both fisheries and escapements (portion of a salmon population that does not get caught in fisheries and returns to its natal river to spawn). In the current study of southern British Columbia coho salmon (Oncorhynchus kisutch) populations, PBT analysis provided novel information on intra-population heterogeneity among males in the total number of progeny identified in fisheries and escapements, the proportion of progeny sampled from fisheries versus escapement, the proportion of two-year old progeny (jacks) produced, and the within-season return time of progeny. Fishery recoveries of coho salmon revealed heterogeneity in migration patterns among and within populations, with recoveries from north and central coast fisheries distinguishing ‘northern migrating’ from ‘resident’ populations. In northern-migrating populations, the mean distance between fishery captures of sibs (brothers and sisters) was significantly less than the mean distance between non-sibs, indicating the possible presence of intra-population genetic heterogeneity for migration pattern. Variation among populations in productivity and within populations in fish catchability indicated that population selection and broodstock management can be implemented to optimize harvest benefits from hatcheries. Application of PBT provided valuable information for assessment and management of hatchery-origin coho salmon in British Columbia.
Contributors:Sigurdsson H.B., Briem K.
Background: Biomechanical studies of ACL injury risk factors frequently analyze only a fraction of the relevant data, and typically not in accordance with the injury mechanism. Extracting a peak value within a time series of relevance to ACL injuries is challenging due to differences in the relative timing and size of the peak value of interest.
Aims/hypotheses: The aim was to cluster analyze the knee valgus moment time series curve shape in the early stance phase. We hypothesized that 1a) There would be few discrete curve shapes, 1b) there would be a shape reflecting an early peak of the knee valgus moment, 2a) youth athletes of both sexes would show similar frequencies of early peaks, 2b) adolescent girls would have greater early peak frequencies.
Methods: N = 213 (39% boys) youth soccer and team handball athletes (phase 1) and N = 35 (45% boys) with 5 year follow-up data (phase 2) were recorded performing a change of direction task with 3D motion analysis and a force plate. The time series of the first 30% of stance phase were cluster analyzed based on Euclidean distances in two steps; shape-based main clusters with a transformed time series, and magnitude based sub-clusters with body weight normalized time series. Group differences (sex, phase) in curve shape frequencies, and shape-magnitude frequencies were tested with chi-squared tests.
Results: Six discrete shape-clusters and 14 magnitude based sub-clusters were formed. Phase 1 boys had greater frequency of early peaks than phase 1 girls (38% vs 25% respectively, P < 0.001 for full test). Phase 2 girls had greater frequency of early peaks than phase 2 boys (42% vs 21% respectively, P < 0.001 for full test).
Conclusions: Cluster analysis can reveal different patterns of curve shapes in biomechanical data, which likely reflect different movement strategies. The early peak shape is relatable to the ACL injury mechanism as the timing of its peak moment is consistent with the timing of injury. Greater frequency of early peaks demonstrated by Phase 2 girls is consistent with their higher risk of ACL injury in sports.
Contributors:Meade, Lara, Finnegan, Sam, Kad, Ridhima, Fowler, Kevin, Pomiankowski, Andrew
Selfish genetic elements that gain a transmission advantage through the destruction of sperm have grave implications for drive male fertility. In the X-linked SR meiotic drive system of a stalk-eyed fly, we found that drive males have greatly enlarged testes and maintain high fertility despite the destruction of half their sperm, even when challenged with fertilising large numbers of females. Conversely, we observed reduced allocation of resources to the accessory glands that probably explains the lower mating frequency of SR males. Body size and eyespan were also reduced, which are likely to impair viability and pre-copulatory success. We discuss the potential evolutionary causes of these differences between drive and standard males.