The opportunity for sexual selection: not mismeasured, just misunderstood

Evolutionary biologists have developed several indices, such as selection gradients (β) and the opportunity for sexual selection (I_s), to quantify the actual and/or potential strength of sexual selection acting in natural or experimental populations. In a recent paper, Klug et al. (J. Evol. Biol. 23 , 2010, 447) contend that selection gradients are the only legitimate metric for quantifying sexual selection. They argue that I_s and similar mating‐system‐based metrics provide unpredictable results, which may be uncorrelated with selection acting on a trait, and should therefore be abandoned. We find this view short‐sighted and argue that the choice of metric should be governed by the research question at hand. We describe insights that measures such as the opportunity for selection can provide and also argue that Klug et al. have overstated the problems with this approach while glossing over similar issues with the interpretation of selection gradients. While no metric perfectly characterizes sexual selection in all circumstances, thoughtful application of existing measures has been and continues to be informative in evolutionary studies.     

Predicting fine‐scale distributions of peripheral aquatic species in headwater streams

Headwater species and peripheral populations that occupy habitat at the edge of a species range may hold an increased conservation value to managers due to their potential to maximize intraspecies diversity and species' adaptive capabilities in the context of rapid environmental change. The southern Appalachian Mountains are the southern extent of the geographic range of native Salvelinus fontinalis and naturalized Oncorhynchus mykiss and Salmo trutta in eastern North America. We predicted distributions of these peripheral, headwater wild trout populations at a fine scale to serve as a planning and management tool for resource managers to maximize resistance and resilience of these populations in the face of anthropogenic stressors. We developed correlative logistic regression models to predict occurrence of brook trout, rainbow trout, and brown trout for every interconfluence stream reach in the study area. A stream network was generated to capture a more consistent representation of headwater streams. Each of the final models had four significant metrics in common: stream order, fragmentation, precipitation, and land cover. Strahler stream order was found to be the most influential variable in two of the three final models and the second most influential variable in the other model. Greater than 70% presence accuracy was achieved for all three models. The underrepresentation of headwater streams in commonly used hydrography datasets is an important consideration that warrants close examination when forecasting headwater species distributions and range estimates. Additionally, it appears that a relative watershed position metric (e.g., stream order) is an important surrogate variable (even when elevation is included) for biotic interactions across the landscape in areas where headwater species distributions are influenced by topographical gradients.     

Productivity and significance of headwater streams: population structure and biomass of the black-bellied salamander (Desmognathus quadramaculatus)

1. Headwater streams are a significant feature of the southern Appalachian landscape, comprising more than 70% of the total stream length in the region. Salamanders are the dominant vertebrate within headwater‐riparian forest ecosystems, but their ecological role is not clearly understood. 2. We studied a population of black‐bellied salamanders (Desmognathus quadramaculatus) at a headwater stream in the southern Appalachian Mountains using radio‐telemetry and mark‐recapture methods. The length and area of headwater streams in the region were estimated using GIS. 3. Home ranges of radio‐tracked salamanders were relatively small (mean = 1.06 m²). Adult salamanders in our telemetry study inhabited edge microhabitats significantly more often than either stream or riparian microhabitats, and the same trend was observed in the mark‐recapture study. 4. We estimated the population density at this site to be 11 294 salamanders ha^?1, amounting to 99.30 kg ha^?1 of biomass, an estimate that is six times greater than reported in previous studies. The majority of this biomass was found within the stream, but 22% was found in the surrounding riparian habitat more than 1 m from the stream. Using headwater stream length and area estimates, we extrapolated biomass estimates for black‐bellied salamanders inhabiting stream and riparian microhabitats across the study region. 5. We report one of the largest estimates of secondary consumer biomass for a headwater ecosystem, attesting to the overall productivity of headwater streams. Headwaters are known to be important for ecological and ecosystem processes and our biomass estimates suggest that salamanders are a critical component to these systems.     

Conservation in a cup of water: estimating biodiversity and population abundance from environmental DNA

Three mantras often guide species and ecosystem management: (i) for preventing invasions by harmful species, ‘early detection and rapid response’; (ii) for conserving imperilled native species, ‘protection of biodiversity hotspots’; and (iii) for assessing biosecurity risk, ‘an ounce of prevention equals a pound of cure.’ However, these and other management goals are elusive when traditional sampling tools (e.g. netting, traps, electrofishing, visual surveys) have poor detection limits, are too slow or are not feasible. One visionary solution is to use an organism’s DNA in the environment (eDNA), rather than the organism itself, as the target of detection. In this issue of Molecular Ecology, Thomsen et al. (2012) provide new evidence demonstrating the feasibility of this approach, showing that eDNA is an accurate indicator of the presence of an impressively diverse set of six aquatic or amphibious taxa including invertebrates, amphibians, a fish and a mammal in a wide range of freshwater habitats. They are also the first to demonstrate that the abundance of eDNA, as measured by qPCR, correlates positively with population abundance estimated with traditional tools. Finally, Thomsen et al. (2012) demonstrate that next‐generation sequencing of eDNA can quantify species richness. Overall, Thomsen et al. (2012) provide a revolutionary roadmap for using eDNA for detection of species, estimates of relative abundance and quantification of biodiversity.     

Searching for sex‐reversals to explain population demography and the evolution of sex chromosomes

Sex determination can be purely genetic (as in mammals and birds), purely environmental (as in many reptiles), or genetic but reversible by environmental factors during a sensitive period in life, as in many fish and amphibians ( Wallace et al. 1999 ; Baroiller et al. 2009a ; Stelkens & Wedekind 2010 ). Such environmental sex reversal (ESR) can be induced, for example, by temperature changes or by exposure to hormone‐active substances. ESR has long been recognized as a means to produce more profitable single‐sex cultures in fish farms ( Cnaani & Levavi‐Sivan 2009 ), but we know very little about its prevalence in the wild. Obviously, induced feminization or masculinization may immediately distort population sex ratios, and distorted sex ratios are indeed reported from some amphibian and fish populations ( Olsen et al. 2006 ; Alho et al. 2008 ; Brykov et al. 2008 ). However, sex ratios can also be skewed by, for example, segregation distorters or sex‐specific mortality. Demonstrating ESR in the wild therefore requires the identification of sex‐linked genetic markers (in the absence of heteromorphic sex chromosomes) followed by comparison of genotypes and phenotypes, or experimental crosses with individuals who seem sex reversed, followed by sexing of offspring after rearing under non‐ESR conditions and at low mortality. In this issue, Alho et al. (2010) investigate the role of ESR in the common frog (Rana temporaria) and a population that has a distorted adult sex ratio. They developed new sex‐linked microsatellite markers and tested wild‐caught male and female adults for potential mismatches between phenotype and genotype. They found a significant proportion of phenotypic males with a female genotype. This suggests environmental masculinization, here with a prevalence of 9%. The authors then tested whether XX males naturally reproduce with XX females. They collected egg clutches and found that some had indeed a primary sex ratio of 100% daughters. Other clutches seemed to result from multi‐male fertilizations of which at least one male had the female genotype. These results suggest that sex‐reversed individuals affect the sex ratio in the following generation. But how relevant is ESR if its prevalence is rather low, and what are the implications of successful reproduction of sex‐reversed individuals in the wild?     

Genetics of personalities: no simple answers for complex traits

Identifying the genes that underlie phenotypic variation in natural populations, and assessing the consequences of polymorphisms at these loci for individual fitness are major objectives in evolutionary biology. Yet, with the exception of a few success stories, little progress has been made, and our understanding of the link between genotype and phenotype is still in its infancy. For example, although body length in humans is largely genetically determined, with heritability estimates greater than 0.8, massive genome‐wide association studies (GWAS) have only been able to account for a very small proportion of this variation ( Gudbjartsson et al. 2008 ). If it is so difficult to explain the genetics behind relatively ‘simple’ traits, can we envision that it will at all be possible to find genes underlying complex behavioural traits in wild non‐model organisms? Some notable examples suggest that this can indeed be a worthwhile endeavour. Recently, the circadian rhythm gene Clock has been associated with timing of breeding in a wild blue tit population ( Johnsen et al. 2007 ; Liedvogel et al. 2009 ) and the Pgi gene to variation in dispersal and flight endurance in Glanville fritillary butterflies ( Niitepold et al. 2009 ). A promising candidate gene for influencing complex animal personality traits, also known as behavioural syndromes ( Sih et al. 2004 ), is the dopamine receptor D4 (DRD4) gene. Within the last decade, polymorphisms in this gene have been associated with variation in novelty seeking and exploration behaviour in a range of species, from humans to great tits ( Schinka et al. 2002 ; Fidler et al. 2007 ). In this issue, Korsten et al. (2010) attempt to replicate this previously observed association in wild‐living birds, and test for the generality of the association between DRD4 and personality across a number of European great tit populations.     

Within-genotype epigenetic variation enables broad niche width in a flower living yeast

Niche theory is one of the central organizing concepts in ecology. Generally, this theory defines a given species niche as all of the factors that effect the persistence of the species as well as the impact of the species in a given location ( Hutchinson 1957 ; Chase 2011 ). Many studies have argued that phenotypic plasticity enhances niche width because plastic responses allow organisms to express advantageous phenotypes in a broader range of environments ( Bradshaw 1965 ; Van Valen 1965 ; Sultan 2001 ). Further, species that exploit habitats with fine‐grained variation, or that form metapopulations, are expected to develop broad niche widths through phenotypic plasticity ( Sultan & Spencer 2002 ; Baythavong 2011 ). Although a long history of laboratory, greenhouse and reciprocal transplant experiments have provided insight into how plasticity contributes to niche width ( Pigliucci 2001 ), recent advances in molecular approaches allow for a mechanistic understanding of plasticity at the molecular level ( Nicotra et al. 2010 ). In particular, variation in epigenetic effects is a potential source of the within‐genotype variation that underlies the phenotypic plasticity associated with broad niche widths. Epigenetic mechanisms can alter gene expression and function without altering DNA sequence ( Richards 2006 ) and may be stably transmitted across generations ( Jablonka & Raz 2009 ; Verhoeven et al. 2010 ). Also, epigenetic mechanisms may be an important component of an individual’s response to the environment ( Verhoeven et al. 2010 ). While these ideas are intriguing, few studies have made a clear connection between genome‐wide DNA methylation patterns and phenotypic plasticity (e.g. Bossdorf et al. 2010 ). In this issue of Molecular Ecology, Herrera et al. (2012) present a study that demonstrates epigenetic changes in genome‐wide DNA methylation are causally active in a species’ ability to exploit resources from a broad range of environments and are particularly important in harsh environments.     

Amphibians as metrics of critical biological thresholds in forested headwater streams of the Pacific Northwest, U.S.A.

1. Amphibians are recognized both for their sensitivity to environmental perturbations and for their usefulness as cost-effective biometrics of ecosystem integrity (=system health).
2. Twenty-three years of research in headwater streams in the Klamath-Siskiyou and North Coast Bioregions of the Pacific Northwest, U.S.A., showed distinct patterns in the distribution of amphibians to variations in water temperature, % fine sediments and the amount of large woody debris (LWD).
3. Here, we review seven studies that demonstrate connections between species presence and abundance and these three in-stream variables. These data were then used to calculate realized niches for three species, the southern torrent salamander, the larval coastal tailed frog and the larval coastal giant salamander, relative to two of these environmental stressors (water temperature and % fine sediments). Moreover, multivariate generalized additive models were used to predict the presence of these three amphibians when these three stressors act in concert.
4. Stream-dwelling amphibians are shown to be extremely sensitive to changes in water temperature, amounts of fine sediment and LWD, and specific thresholds and ranges for a spectrum of animal responses can be used to manage for headwater tributary ecosystem integrity.
5. Consequently, amphibians can provide a direct metric of stream ecosystem integrity acting as surrogates for the ability of a stream network to support other stream-associated biota, such as salmonids, and their related ecological services.     

Cosmopolitanism of microbial eukaryotes in the global deep seas

Deep sea environments cover more than 65% of the earth’s surface and fulfil a range of ecosystem functions, yet they are also amongst the least known habitats on earth. Whilst the discovery of key geological processes, combined with technological developments, has focused interest onto geologically active areas such as hydrothermal vents, most abyssal biodiversity remains to be discovered ( Danovaro et al. 2010 ). However, as for terrestrial reservoirs of biodiversity, the world’s largest biome is under threat from anthropogenic activities ranging from environmental change to the exploitation of minerals and rare‐earth elements ( Kato et al. 2011 ). It is therefore important to understand the magnitude, nature and composition of deep sea biological communities to inform us of levels of local adaptation, functionality and resilience with respect to future environmental perturbation. In this issue of Molecular Ecology, Bik et al. utilize 454 Roche metagenetic environmental sequencing to assess microbial metazoan community composition and phylogenetic identity across deep sea depth gradients and between ocean basins. The analyses suggest that although the majority of microbial eukaryotic taxa are regionally restricted, a small percentage might maintain cosmopolitan deep sea distributions, and an even smaller fraction appear to be eurybathic (live across depth gradients).     

Forest succession and prey availability influence the strength and scale of terrestrial‐aquatic linkages in a headwater salamander system

1. Trophic linkages between terrestrial and aquatic ecosystems are common and sensitive to disruption. However, there is little information on what causes variation in the strength and spatial scale of these linkages. 2. In the highly aquatic adults of the headwater salamander Gyrinophilus porphyriticus (family Plethodontidae), use of terrestrial prey decreases along a gradient from early‐ to late‐successional riparian forests. To understand the cause of this relationship, we tested the predictions that (i) terrestrial prey abundance is lower in late‐successional forests, and (ii) G. porphyriticus adults cannot move as far from the stream to forage in late‐successional forests, thus limiting access to terrestrial prey. 3. We established 100‐m long study reaches on six headwater streams in the Hubbard Brook Experimental Forest, New Hampshire. Three reaches were in early‐successional forests and three were in late‐successional forests. We conducted pitfall trapping for invertebrate prey in June and July of 2005, with three traps at 0, 2, 5 and 10 m from the stream at each reach. In June, July and August of 2004 and 2005, nighttime salamander surveys were conducted at each reach along ten, 10‐m long by 2.5‐m wide transects perpendicular to the stream. 4. Abundance of terrestrial prey was consistently lower in late‐successional forests, suggesting that consumption of terrestrial prey by G. porphyriticus is affected by prey abundance. Contrary to our prediction, G. porphyriticus adults moved farther from the stream in late‐successional forests, suggesting that habitat conditions in late‐successional forests do not limit movement away from the stream, and that lower abundances of terrestrial prey in these forests may cause salamanders to move farther from streams. 5. Our results provide novel insight on the extent of terrestrial habitat use by G. porphyriticus. More broadly, these results indicate that major habitat gradients, such as forest succession, can affect the strength and scale of terrestrial‐aquatic linkages. Application of this insight to the design of vegetation buffers along headwater streams would have widespread benefits to freshwater ecosystems.     

Effects of Stream Restoration on Woody Riparian Vegetation of Southern Appalachian Mountain Streams,North Carolina,U.S.A

Riparian revegetation, such as planting woody seedlings or live stakes, is a nearly ubiquitous component of stream restoration projects in the United States. Though evaluations of restoration success usually focus on in‐stream ecosystems, in order to understand the full impacts of restoration the effects on riparian ecosystems themselves must be considered. We examined the effects of stream restoration revegetation measures on riparian ecosystems of headwater mountain streams in forested watersheds by comparing riparian vegetation structure and composition at reference, restored, and degraded sites on nine streams. According to mixed model analysis of variance (ANOVA), there was a significant effect of site treatment on riparian species richness, basal area, and canopy cover, but no effect on stem density. Vegetation characteristics at restored sites differed from those of reference sites according to all metrics (i.e. basal area, canopy cover, and species composition) except species richness and stem density. Restored and degraded sites were structurally similar, with some overlap in species composition. Restored sites were dominated by Salix sericea and Cornus amomum (species commonly planted for revegetation) and a suite of disturbance‐adapted species also dominant at degraded sites. Differences between reference and restored sites might be due to the young age of restored sites (average 4 years since restoration), to reassembly of degraded site species composition at restored sites, or to the creation of a novel anthropogenic ecosystem on these headwater streams. Additional research is needed to determine if this anthropogenic riparian community type persists as a resilient novel ecosystem and provides valued riparian functions.     

Speciation genetics of biological invasions with hybridization

The negative effects of human‐induced habitat disturbance and modification on multiple dimensions of biological diversity are well chronicled ( Turner 1996 ; Harding et al. 1998 ; Lawton et al. 1998 ; Sakai et al. 2001 ). Among the more insidious consequences is secondary contact between formerly allopatric taxa ( Anderson & Hubricht 1938 ; Perry et al. 2002 ; Seehausen 2006 ). How the secondary contact will play out is unpredictable ( Ellstrand et al. 2010 ), but if the taxa are not fully reproductively isolated, hybridization is likely, and if the resulting progeny are fertile, the eventual outcome is often devastating from a conservation perspective ( Rhymer & Simberloff 1996 ; Wolf et al. 2001 ; McDonald et al. 2008 ). In this issue of Molecular Ecology, Steeves et al. (2010) present an analysis of hybridization between two avian species, one of which is critically endangered and the other of which is invasive. Their discovery that the endangered species has not yet been hybridized to extinction is promising and not what one would necessarily expect from theory.     

Loss of intestinal nuclei and intestinal integrity in aging C. elegans

The roundworm C. elegans is widely used as an aging model, with hundreds of genes identified that modulate aging (Kaeberlein et al., 2002. Mech. Ageing Dev. 123 , 1115–1119). The development and bodyplan of the 959 cells comprising the adult have been well described and established for more than 25 years ( Sulston & Horvitz, 1977 . Dev. Biol. 56 , 110–156; Sulston et al., 1983. Dev. Biol. 100 , 64–119.). However, morphological changes with age in this optically transparent animal are less well understood, with only a handful of studies investigating the pathobiology of aging. Age‐related changes in muscle ( Herndon et al., 2002 . Nature 419 , 808–814), neurons ( Herndon et al., 2002 ), intestine and yolk granules ( Garigan et al., 2002 . Genetics 161 , 1101–1112; Herndon et al., 2002 ), nuclear architecture ( Haithcock et al., 2005 . Proc. Natl Acad. Sci. USA 102 , 16690–16695), tail nuclei ( Golden et al., 2007 . Aging Cell 6 , 179–188), and the germline ( Golden et al., 2007 ) have been observed via a variety of traditional relatively low‐throughput methods. We report here a number of novel approaches to study the pathobiology of aging C. elegans. We combined histological staining of serial‐sectioned tissues, transmission electron microscopy, and confocal microscopy with 3D volumetric reconstructions and characterized age‐related morphological changes in multiple wild‐type individuals at different ages. This enabled us to identify several novel pathologies with age in the C. elegans intestine, including the loss of critical nuclei, the degradation of intestinal microvilli, changes in the size, shape, and cytoplasmic contents of the intestine, and altered morphologies caused by ingested bacteria. The three‐dimensional models we have created of tissues and cellular components from multiple individuals of different ages represent a unique resource to demonstrate global heterogeneity of a multicellular organism.     

APPLIED ISSUES: Exploring the response of functional indicators of stream health to land‐use gradients

1. Broad‐scale assessment of stream health is often based on correlative relationships between catchment land‐use categories and measurements of stream biota or water chemistry. Few studies have attempted to characterise the response curves that describe how measures of ecosystem function change along gradients of catchment land use, or explored how these responses vary at broad spatial scales. 2. In autumn 2008, we conducted a survey of 84 streams in three bioregions of New Zealand to assess the sensitivity of functional indicators to three land‐use gradients: percentage of native vegetation cover, percentage of impervious cover (IC) and predicted nitrogen (N) concentration. We examined these relationships using general linear models and boosted regression trees to explore monotonic, non‐monotonic and potential threshold components of the response curves. 3. When viewing the responses to individual land‐use gradients, four of five functional indicators were positively correlated with the removal of native vegetation cover and N. In general, weaker and less responsive models were observed for the IC gradient. An analysis of the response to multiple stressors showed δ¹⁵N of primary consumers and gross primary productivity (GPP) to be the most responsive functional indicators to land‐use gradients. The multivariate models identified thresholds for change in the relationship between the functional indicators and all three land‐use gradients. Apparent thresholds were <10%IC, between 40 and 80% loss of native vegetation cover and at 0.5 and 3.2 mg L^?1 N. 4. The strength of regression models and the nature of the response curves suggest that measures of ecosystem function exhibit predictable relationships with land use. Furthermore, the responses of functional indicators varied little among three bioregions. This information provides a strong argument for the inclusion of functional indicators in a holistic assessment of stream health.     

ITS, OTUs and beyond—fungal hyperdiversity calls for supplementary solutions

Molecular species recognition of fungi emerged years before DNA barcoding ( Seifert 2009 ). While the ideal fungal DNA barcode seems Utopian, two research decades nevertheless highlight the internal transcribed spacer (ITS) as the best available choice ( Seifert 2009 ). Databases providing reliable ITS sequences of known fungi require enormous efforts, but are urgently needed ( Abarenkov et al. 2010a,b ; Begerow et al. 2010 ). Any criticism of such a commitment seems unjustified. However, exclusive focus on the development of ITS reference libraries will delay the progress towards a deeper ecological insight. It is widely acknowledged that ITS fails to recognize species, particularly in some ascomycete lineages ( Balajee et al. 2009 ; Seifert 2009 ). It also appears paradoxical to solely rely on ITS for ecological recognition of fungal species when modern fungal systematics rely on phylogenetic species recognition with concordance of multiple gene genealogies (see Blackwell 2011 ). Considering that at least 98% of the predicted ～5 million fungal species remain undescribed ( Blackwell 2011 ), how will reliance on ITS alone influence the biodiversity estimates and ecological understanding? In this issue, Gazis et al. (2011) elegantly demonstrate through multi‐locus sequence phylogeny analyses that ITS largely underestimates the species diversity of tropical fungal endophytes and even more importantly obscures fundamental ecological and biogeographical patterns. This thorough reflection on species delimitation criteria and their implications for ecological and biogeographical inferences underline that ITS, particularly in hyperdiverse habitats, provides no shortcut to deeper knowledge of fungal ecology.     

Is The Amphibian Tree of Life really fatally flawed?

Wiens (2007 , Q. Rev. Biol. 82, 55–56) recently published a severe critique of Frost et al.'s (2006, Bull. Am. Mus. Nat. Hist. 297, 1–370) monographic study of amphibian systematics, concluding that it is “a disaster” and recommending that readers “simply ignore this study”. Beyond the hyperbole, Wiens raised four general objections that he regarded as “fatal flaws”: (1) the sampling design was insufficient for the generic changes made and taxonomic changes were made without including all type species; (2) the nuclear gene most commonly used in amphibian phylogenetics, RAG‐1, was not included, nor were the morphological characters that had justified the older taxonomy; (3) the analytical method employed is questionable because equally weighted parsimony “assumes that all characters are evolving at equal rates”; and (4) the results were at times “clearly erroneous”, as evidenced by the inferred non‐monophyly of marsupial frogs. In this paper we respond to these criticisms. In brief: (1) the study of Frost et al. did not exist in a vacuum and we discussed our evidence and evidence previously obtained by others that documented the non‐monophyletic taxa that we corrected. Beyond that, we agree that all type species should ideally be included, but inclusion of all potentially relevant type species is not feasible in a study of the magnitude of Frost et al. and we contend that this should not prevent progress in the formulation of phylogenetic hypotheses or their application outside of systematics. (2) Rhodopsin, a gene included by Frost et al. is the nuclear gene that is most commonly used in amphibian systematics, not RAG‐1. Regardless, ignoring a study because of the absence of a single locus strikes us as unsound practice. With respect to previously hypothesized morphological synapomorphies, Frost et al. provided a lengthy review of the published evidence for all groups, and this was used to inform taxonomic decisions. We noted that confirming and reconciling all morphological transformation series published among previous studies needed to be done, and we included evidence from the only published data set at that time to explicitly code morphological characters (including a number of traditionally applied synapomorphies from adult morphology) across the bulk of the diversity of amphibians (Haas, 2003, Cladistics 19, 23–90). Moreover, the phylogenetic results of the Frost et al. study were largely consistent with previous morphological and molecular studies and where they differed, this was discussed with reference to the weight of evidence. (3) The claim that equally weighted parsimony assumes that all characters are evolving at equal rates has been shown to be false in both analytical and simulation studies. (4) The claimed “strong support” for marsupial frog monophyly is questionable. Several studies have also found marsupial frogs to be non‐monophyletic. Wiens et al. (2005, Syst. Biol. 54, 719–748) recovered marsupial frogs as monophyletic, but that result was strongly supported only by Bayesian clade confidence values (which are known to overestimate support) and bootstrap support in his parsimony analysis was < 50%. Further, in a more recent parsimony analysis of an expanded data set that included RAG‐1 and the three traditional morphological synapomorphies of marsupial frogs, Wiens et al. (2006, Am. Nat. 168, 579–596) also found them to be non‐monophyletic. Although we attempted to apply the rule of monophyly to the naming of taxonomic groups, our phylogenetic results are largely consistent with conventional views even if not with the taxonomy current at the time of our writing. Most of our taxonomic changes addressed examples of non‐monophyly that had previously been known or suspected (e.g., the non‐monophyly of traditional Hyperoliidae, Microhylidae, Hemiphractinae, Leptodactylidae, Phrynobatrachus, Ranidae, Rana, Bufo; and the placement of Brachycephalus within “Eleutherodactylus”, and Lineatriton within “Pseudoeurycea”), and it is troubling that Wiens and others, as evidenced by recent publications, continue to perpetuate recognition of non‐monophyletic taxonomic groups that so profoundly misrepresent what is known about amphibian phylogeny. © The Willi Hennig Society 2007.     

North Atlantic marine communities through time

How and why ecological communities change their species membership over time and space is a central issue in ecology and evolution. Phylogeographic approaches based on animal mitochondrial DNA sequences have been important for revealing historical patterns of individual species and can provide qualitative comparisons among species. Exciting new methods, particularly implementing approximate Bayesian computation (ABC – Beaumont et al. 2002 ), now allow model‐based quantitative comparisons among species and permit the probabilistic exploration of alternative community‐level hypotheses (see review by Hickerson et al. 2010 ). In this issue of Molecular Ecology, Ilves et al. (2010) use an ABC approach to bring fresh insights into the well‐studied question of how North Atlantic coastal species contracted and expanded their ranges in response to late Pleistocene/Holocene climate fluctuations.     

Invertebrate assemblages of pools in arid‐land streams have high functional redundancy and are resistant to severe drying

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Loss of genetic diversity in the North American mayfly Ephemerella invaria associated with deforestation of headwater streams

1. Terrestrial dispersal by aquatic insects increases population connectivity in some stream species by allowing individuals to move outside the structure of the stream network. In addition, individual survival and reproductive success (as well as dispersal) are tightly linked to the quality of the terrestrial habitat. 2. In historically forested catchments, deforestation and altered land use have the potential to interfere with mayfly dispersal or mating behaviours by degrading the quality of the terrestrial matrix among headwater streams. We hypothesised that loss of tree cover in first‐order catchments would be associated with an increase in population substructure and a decrease in genetic diversity of mayfly populations. 3. To test this hypothesis, we investigated spatial patterns of genetic variation in the common mayfly Ephemerella invaria across a gradient of deforestation in the central piedmont region of eastern United States. Intraspecific genetic diversity and population substructure were estimated from data obtained using fluorescent amplified fragment length polymorphism (AFLP) markers. 4. We found that mayfly populations had low population substructure within headwater stream networks and that genetic diversity was strongly negatively correlated with mean deforestation of the first‐order catchments. The large‐scale pattern of population substructure followed a pattern of isolation by distance (IBD) in which genetic differentiation increases with geographical distance, but assignment tests placed a few individuals into populations 300 km away from the collection site. 5. Our results show that loss of genetic diversity in this widespread aquatic insect species is co‐occurring with deforestation of headwater streams. 6. Most arguments supporting protection of headwater streams in the United States have centred on the role of these streams as hydrological and biogeochemical conduits to downstream waters. Our work suggests that headwater stream land use, and specifically tree cover, may have a role in the maintenance of regional genetic diversity in some common aquatic insect species.