Do life history traits predict responses to defoliation in co‐occurring prairie grasses?

Abstract. This study examines whether competition between the unpalatable grass Hilaria mutica and three co‐occurring, palatable grasses in a Texan mixed prairie is altered by non‐selective or selective defoliation. In this four‐year study, plants were grown in monoculture or in combination with the unpalatable Hilaria in a replacement design. Under no defoliation, the unpalatable Hilaria had a lower growth potential than Bouteloua curtipendula and Nassella leucotricha that were of equal stature, and produced only as much as the shorter grass, Buchloe dactyloides. Bouteloua had the highest growth potential under no‐defoliation and was defoliation tolerant, except when defoliated at ground level. Nassella was more productive than the unpalatable Hilaria, since the ability to grow earlier in the year enabled it to compete successfully with Hilaria. These results indicate that with adequate deferment Bouteloua and Nassella should compete successfully with Hilaria and Buchloe should be able to maintain itself in the presence of Hilaria. Under non‐selective defoliation, Hilaria was able to compete successfully only with Buchloe. Hilaria was sensitive to defoliation, despite being rhizomatous, and competed less successfully with Buchloe after non‐selective defoliation than it did when not defoliated. This indicates that the management practice of burning and stocking heavily with livestock until Hilaria is avoided, resulting in non‐selective defoliation, will not cause Hilaria to be more competitive with the more palatable Bouteloua, Buchloe or Nassella. Hilaria was able to compete most successfully under selective defoliation when it was not defoliated. Under selective defoliation, by avoiding herbivory, Hilaria is able to compete strongly with at least Buchloe and Nassella. The reaction of Nassella and Buchloe to selective defoliation indicates that they may have been displaced by Hilaria in the past. In contrast, under the short‐term and non‐limiting growth conditions of this study, Bouteloua competed successfully with Hilaria even under selective defoliation. These results do not rule out the possibility that, through selective defoliation, Hilaria may have displaced other grasses including Bouteloua in the past.     

Do human ‘life history strategies’ exist?

Interest in incorporating life history research from evolutionary biology into the human sciences has grown rapidly in recent years. Two core features of this research have the potential to prove valuable in strengthening theoretical frameworks in the health and social sciences: the idea that there is a fundamental trade-off between reproduction and health; and that environmental influences are important in determining how life histories develop. However, the literature on human life histories has increasingly travelled away from its origins in biology, and become conceptually diverse. For example, there are differences of opinion between evolutionary researchers about the extent to which behavioural traits associate with life history traits to form ‘life history strategies’. Here, I review the different approaches to human life histories from evolutionary anthropologists, developmental psychologists and personality psychologists, in order to assess the evidence for human ‘life history strategies’. While there is precedent in biology for the argument that some behavioural traits, notably risk-taking behaviour, may be linked in predictable ways with life history traits, there is little theoretical or empirical justification for including a very wide range of behavioural traits in a ‘life history strategy’. Given the potential of life history approaches to provide a powerful theoretical framework for understanding human health and behaviour, I then recommend productive ways forward for the field: 1) greater focus on the life history trade-offs which underlie proposed strategies; 2) greater precision when using the language of life history theory and life history strategies; 3) collecting more empirical data, from a diverse range of populations, on linkages between life history traits, behavioural traits and the environment, including the underlying mechanisms which generate these linkages; and 4) greater integration with the social and health sciences.     

Consequences of extreme life history traits on population persistence: do short-lived gobies face demographic bottlenecks?

The majority of coral reef goby species are short-lived, with some highly abundant species living less than 100 d. To understand the role and consequences of this extreme life history in shaping coral reef fish populations, we quantitatively documented the structure of small reef fish populations over a 26-month period (>14 short-lived fish generations) at an inshore reef on the Great Barrier Reef, Australia. Most species with life spans >1 yr, such as pomacentrids, exhibited a peak in recruitment during the austral summer, driving seasonal changes in the small fish community composition. In contrast, there were no clear changes in goby community composition, despite the abundance of short-lived, high turnover species. Species of Eviota, the most abundant gobiid genus observed, showed remarkably similar demographic profiles year-round, with consistent densities of adults as well as recently recruited juveniles. Our results demonstrate ongoing recruitment of these small cryptic fishes, which appears to compensate for an exceptionally short life span on the reef. Our results suggest that gobiid populations are able to overcome demographic limitations, and by maintaining reproduction, larval survival and recruitment throughout the year, they may avoid population bottlenecks. These findings also underline the potential trophodynamic importance of these small species; because of this constant turnover, Eviota species and other short-lived fishes may be particularly valuable contributors to the flow of energy on coral reefs, underpinning the year-round trophic structure.     

Do lichens show latitudinal patterns of diversity?

No previous study has directly investigated whether lichens show latitudinal patterns of diversity. We used vouchered data and MaxEnt models to compile richness estimates (species, genera, and families) across the western coastal region of the US. Nonparametric multiplicative regression then sought the geographic factors or interactions of factors that explained the most variability in lichen richness. Collection density was the strongest predictor of raw estimates of richness at all taxonomic ranks. Latitude was the overall single-best predictor of MaxEnt modeled species, generic, and familial richness in all models. MaxEnt modeling was necessary to minimize collection bias, which otherwise obscured any other patterns of diversity. While geography explained a sizable portion of variance in lichen richness, it does not trend linearly with latitude. Instead, lichen diversity may be influenced by a compilation of regional and local factors including climate, disturbance, and competition.     

Commentary: Do we have a consistent terminology for species diversity? The fallacy of true diversity

There is no single best index that can be used to answer all questions about species diversity. Entropy-based diversity indices, including Hill’s indices, cannot account for geographical and phylogenetic structure. While a single diversity index arises if we impose several constraints—most notably that gamma diversity be completely decomposed into alpha and beta diversity—there are many ecological questions regarding species diversity for which it is counterproductive, requiring decomposability. Non-decomposable components of gamma diversity may quantify important intrinsic ecological properties, such as resilience or nestedness.     

Evaluating genetic resources of forest trees by means of life history traits – a Norwegian example

Additive variation in adaptive traits is a prerequisite for selectionand adaptation to future environmental changes, but distribution of adaptivegenetic variability between and within populations is poorly known in mostforest trees. Owing to this deficiency, life history traits such as geographicrange, pollination vector and seed dispersal capability, which significantlyaffect gene flow and thus the distribution of genetic variability, were used toevaluate the genetic resources in 23 Norwegian native forest tree species. Basedon the combination of life history traits the species' genetic resourceswere classified either as viable, potentially vulnerable or vulnerable, assuminga decrease in within-population variability in this sequence. Twelve widelydistributed species with generally effective dispersal of pollen and seeds wereconsidered viable (Pinus sylvestris, Picea abies,Juniperus communis, Betula pubescens, B. pendula,Alnus incana, A. glutinosa, Salix caprea, Populustremula, Corylus avellana, Sorbus aucuparia, Prunus padus)and have as such no particular conservation needs. Effective seed dispersal of these species, asinferred from post-glacial migration rates, may be partly responsible for theirgenerally early post-glacial appearance, and may, in combination with the wideranges and relatively large evolutionary potential, indicate that viable speciesare best able to cope with climatic change. Among species with restricted rangesand more limited gene flow eight were considered potentially vulnerable (Quercuspetraea, Q. robur, Fraxinus excelsior, Acer platanoides,Taxus baccata, Ilexaquifolium, Fagus sylvatica, Ulmus glabra) and threewere considered vulnerable (Tiliacordata, Malus sylvestris, P. avium). Application of differentintensities of a multiple population breeding system (MPBS) is considered the most appropriate mode of conservinggenetic resources in these species.     

Evolutionary implications of host–pathogen specificity: the fitness consequences of host life history traits

Pathogens and parasites can be strong agents of selection, and often exhibit some degree of genetic specificity for individual host strains. Here we show that this host–pathogen specificity can affect the evolution of host life history traits. All else equal, evolution should select for genes that increase individuals' reproduction rates or lifespans (and thus total reproduction per individual). Using a simple host–pathogen model, we show that when the genetic specificity of pathogen infection is low, host strains with higher reproduction rates or longer lifespans drive slower-reproducing or shorter-lived host strains to extinction, as one would expect. However, when pathogens exhibit specificity for host strains with different life history traits, the evolutionary advantages of these traits can be greatly diminished by pathogen-mediated selection. Given sufficient host–pathogen specificity, pathogen-mediated selection can maintain polymorphism in host traits that are correlated with pathogen resistance traits, despite large intrinsic fitness differences among host strains. These results have two important implications. First, selection on host life history traits will be weaker than expected, whenever host fitness is significantly affected by genotype-specific pathogen attack. Second, where polymorphism in host traits is maintained by pathogen-mediated selection, preserving the genetic diversity of host species may require preserving their pathogens as well. This revised version was published online in November 2006 with corrections to the Cover Date.     

Do functional traits improve prediction of predation rates for a disparate group of aphid predators?

Aphid predators are a systematically disparate group of arthropods united on the basis that they consume aphids as part of their diet. In Europe, this group includes Araneae, Opiliones, Heteroptera, chrysopids, Forficulina, syrphid larvae, carabids, staphylinids, cantharids and coccinellids. This functional group has no phylogenetic meaning but was created by ecologists as a way of understanding predation, particularly for conservation biological control. We investigated whether trait-based approaches could bring some cohesion and structure to this predator group. A taxonomic hierarchy-based null model was created from taxonomic distances in which a simple multiplicative relationship described the Linnaean hierarchies (species, genera, etc.) of fifty common aphid predators. Using the same fifty species, a functional groups model was developed using ten behavioural traits (e.g. polyphagy, dispersal, activity, etc.) to describe the way in which aphids were predated in the field. The interrelationships between species were then expressed as dissimilarities within each model and separately analysed using PROXSCAL, a multidimensional scaling (MDS) program. When ordinated using PROXSCAL and then statistically compared using Procrustes analysis, we found that only 17% of information was shared between the two configurations. Polyphagy across kingdoms (i.e. predatory behaviour across animal, plant and fungi kingdoms) and the ability to withstand starvation over days, weeks and months were particularly divisive within the functional groups model. Confirmatory MDS indicated poor prediction of aphid predation rates by the configurations derived from either model. The counterintuitive conclusion was that the inclusion of functional traits, pertinent to the way in which predators fed on aphids, did not lead to a large improvement in the prediction of predation rate when compared to the standard taxonomic approach.     

Do traits of plant species predict the efficacy of species distribution models for finding new occurrences?

Species distribution models (SDMs) are used to test ecological theory and to direct targeted surveys for species of conservation concern. Several studies have tested for an influence of species traits on the predictive accuracy of SDMs. However, most used the same set of environmental predictors for all species and/or did not use truly independent data to test SDM accuracy. We built eight SDMs for each of 24 plant species of conservation concern, varying the environmental predictors included in each SDM version. We then measured the accuracy of each SDM using independent presence and absence data to calculate area under the receiver operating characteristic curve (AUC) and true positive rate (TPR). We used generalized linear mixed models to test for a relationship between species traits and SDM accuracy, while accounting for variation in SDM performance that might be introduced by different predictor sets. All traits affected one or both SDM accuracy measures. Species with lighter seeds, animal‐dispersed seeds, and a higher density of occurrences had higher AUC and TPR than other species, all else being equal. Long‐lived woody species had higher AUC than herbaceous species, but lower TPR. These results support the hypothesis that the strength of species–environment correlations is affected by characteristics of species or their geographic distributions. However, because each species has multiple traits, and because AUC and TPR can be affected differently, there is no straightforward way to determine a priori which species will yield useful SDMs based on their traits. Most species yielded at least one useful SDM. Therefore, it is worthwhile to build and test SDMs for the purpose of finding new populations of plant species of conservation concern, regardless of these species’ traits.     

More than one `fish kairomone'? Perch and stickleback kairomones affect Daphnia life history traits differently

Life history traits of Daphnia galeata clones were affected differently by kairomones exuded by two species of fish. The exposure to Gasterosteus kairomone resulted in an increase in population intrinsic rate of increase and body growth rate relative to the exposure to Perca kairomone. These differences between fish treatments have not been reported earlier. The results suggest differences between fish kairomones that are not due to concentration effects alone. This raises the possibility that kairomones are cocktails of chemicals rather than a single `fish substance'. It also supports the view the effects of size-selective predation vary depending on the local predator–prey assemblage examined. This finding leads to an additional, previously underestimated but potentially complex aspect in zooplankton ecology.     

How universal are reserve design rules? A test using butterflies and their life history traits

We used butterfly species lists available for a set of 125 Czech Republic National Nature Reserves and Monuments, the highest small‐sized conservation category in the country encompassing practically all biotope types existing in central Europe, to test the validity of generally agreed “reserve design rules” using multivariate ordination analyses. Further, we used ordination analysis of butterfly life history traits to seek for biological mechanisms responsible for butterfly community responses to essentially geometric reserves characteristics. Reserve area, relative perimeter, within reserve habitat heterogeneity, and surrounding landscape compositional and configurational heterogeneity all affected the composition of butterfly assemblages after controlling for effects of geographical position and prevailing biotope type. Species inclining towards large reserves displayed low mobility and high local population density, probably because they require large habitat areas to maintain self‐sustaining populations; such species tend to have restricted distribution in the country and threatened status. Reserves with relatively long boundaries hosted species with high mobility, broad trophic range and long adult period; faunas of such reserves contain high proportions of widespread generalists. Species with narrow trophic ranges inclined towards reserves containing diverse habitats, probably due to requirements for high floristic diversity. Species with short adult flight, low generations number and overwintering in early stages inclined towards reserves situated amidst diverse landscapes, perhaps because such species require finely‐grained mosaics for metapopulation dynamics. Commonly agreed reserve design rules thus hold for Central European butterflies, but different design characteristics are important for individual species, depending on their life histories.     

Testing of life history traits of a soilborne pathogen in vitro: Do characteristics of oospores change according the strains of Aphanomyces euteiches and the host plant infected by the pathogen?

Aphanomyces euteiches is a polyphagous, homothallic soilborne pathogen producing asexual (zoospores) and sexual (oospores) spores. Even if oospores are essential for disease development and survival, to date, no study has focused on the production rates of oospores or the quality of the offspring produced by oospores. In this study, a nonabrasive oospore extraction method from infected roots of leguminous species (pea, faba bean and vetch) was developed. This methodology includes steps of grinding and filtration. The quality of oospores (viable, dormant and dead) was assessed with tetrazolium bromide staining, and germination of oospores was tested using exudates of peas, faba bean and vetch. The average yield of the extraction method was approximately 21%. Staining revealed some differences between strains and between leguminous species. The germination percentage of oospores extracted from pea, faba bean and vetch was 25%, 62% and 70%, respectively, and a significant difference was observed according to the origin of A. euteiches‐inoculated strains. Application of exudates seems to stimulate the germination of oospores (2% for the control, 18% for pea exudates and 1% for vetch exudates). Differences observed between A. euteiches strains and leguminous species indicate that more knowledge concerning the biology of oospores is needed. This will help to better estimate evolution process of the pathogen and manage resistance and crop successions.     

The relationship between geographic range size and life history traits: is biogeographic history uncovered? A test using the Iberian butterflies

The geographic range of a species is influenced by past phylogenetic and biogeographic patterns. However, other historical interactions, including the interplay between life history and geography, are also likely involved. Therefore, the range size of a species can be explained on the basis of niche‐breadth or dispersal related hypotheses, and previous work on European butterflies suggests that both, under the respective guise of ecological specialisation and colonising ability may apply. In the present study, data from 205 species of butterflies from the Iberian peninsula were processed through multiple regression analyses to test for correlations between geographic range size, life history traits and geographic features of the species distribution types. In addition, the percentage of variance explained by the subsets of variables analyzed in the study, with and without control for phylogenetic effects was tested. Despite a complex pattern of bivariate correlations, we found that larval polyphagy was the single best correlate of range size, followed by dispersal. Models that combined both life history traits and geographic characteristics performed better than models generated independently. The combined variables explained at least 39% of the variance. Bivariate correlations between range size and body size, migratory habits or egg size primarily reflected taxonomic patterning and reciprocal correlations with larval diet breadth and adult phenology. Therefore, aspects of niche breadth i.e. potential larval diet breadth emerged as the most influential determinants of range size. However, the relationships between these types of ecological traits and biogeographic history must still be considered when associations between life history and range size are of interest.     

Do molecular markers reflect patterns of differentiation in adaptive traits of conifers?

We have examined patterns of variation of several kinds of molecular markers (isozymes, RFLPs of ribosomal DNA and anonymous low-copy number DNA, RAPDs and microsatellites) and an adaptive trait [date of bud set in Scots pine (Pinus sylvestris L.)]. The study included Finnish Scots pine populations (from latitude 60°N to 70°N) which experience a steep climatic gradient. Common garden experiments show that these populations are adapted to the location of their origin and genetically differentiated in adaptive quantitative traits, e.g. the date of bud set in first-year seedlings. In the northernmost population, bud set took place about 21 days earlier than in the southernmost population. Of the total variation in bud set, 36.4% was found among the populations. All molecular markers showed high levels of within-population variation, while differentiation among populations was low. Among all the studied markers, microsatellites were the most variable (H_e=0.77). Differences between populations were small, G_ST was less than 0.02. Our study suggests that molecular markers may be poor predictors of the population differentiation of quantitative traits in Scots pine, as exemplified here by bud-set date.     

Do multiple herbivores maintain chemical diversity of Scots pine monoterpenes?

A central issue in our understanding of the evolution of the diversity of plant secondary metabolites (PSMs) is whether or not compounds are functional, conferring an advantage to the plant, or non-functional. We examine the hypothesis that the diversity of monoterpene PSMs within a plant species (Scots pine Pinus sylvestris) may be explained by different compounds acting as defences against high-impact herbivores operating at different life stages. We also hypothesize that pairwise coevolution, with uncorrelated interactions, is more likely to result in greater PSM diversity, than diffuse coevolution. We tested whether up to 13 different monoterpenes in Scots pine were inhibitory to herbivory by slugs (Arion ater), bank voles (Clethrionomys glareolus), red deer (Cervus elaphus) and capercaillie (Tetrao urogallus), each of which attack trees at a different life stage. Plants containing more α-pinene were avoided by both slugs and capercaillie, which may act as reinforcing selective agents for this dominant defensive compound. Herbivory by red deer and capercaillie were, respectively, weakly negatively associated with δ(3)-carene, and strongly negatively correlated with the minor compound β-ocimene. Three of the four herbivores are probably contributory selective agents on some of the terpenes, and thus maintain some, but by no means all, of the phytochemical diversity in the species. The correlated defensive function of α-pinene against slugs and capercaillie is consistent with diffuse coevolutionary processes.     

Do infectious diseases drive MHC diversity?

The primary function of the major histocompatibility complex (MHC) is to allow the immune system to identify infectious pathogens and eliminate them. Infectious diseases are now thought to be the main selection force that drives and maintains the extraordinary diversity of the MHC.     

Are extraversion and openness indicators of a slow life history strategy?

Theory and data generally concur that a slower Life History Strategy (LHS) is associated with higher Conscientiousness, Agreeableness and Emotional Stability. Whether Extraversion and Openness are indicators of a slow LH, or whether they include both fast and slow LH components, remains unresolved. I addressed these questions in two studies: one of university students observed via periodic brief audio recordings during 72 h of their daily lives, and the second a re-analysis of data from Block and Block's (2006) longitudinal study. In both studies, I operationalized LHS as the correlation between an individual's California Q-Sort (CAQ) profile and the slow Life History (SLH) CAQ template created by Sherman et al. (2013) and Dunkel et al. (2015). I calculated Five Factor Model dimension scores using McCrae et al's (1986) method. In both samples, individuals whose CAQ profile more closely resembled the SLH template were higher in Conscientiousness, Agreeableness, and Emotional Stability than those pursuing a faster LHS. Extraversion was unrelated to LHS, while Openness in the Block and Block data set was actually associated with a faster LHS. Analysis of individual CAQ items revealed some differences between the studies. Generally, Extraversion-loading items tapping excitement-seeking and self-dramatization, and Openness-loading items tapping nonconformity, were associated with a faster LHS. Participants in the audio recording study also completed a HEXACO personality inventory and the Arizona Life History Battery. LHS as measured by the ALHB was uncorrelated with LHS as measured by the CAQ. Controlling for Extraversion yielded a significant positive relationship between the two LHS measures, suggesting that their poor convergent validity resulted from differences in their coverage of Extraversion-related content.