Competitor density influences resource defence in a Poeciliid fish

The concept of economic defendability states that individuals will only defend resources when the benefits outweigh the costs. Competitor density is one factor that influences resource defence among fishes, resource defence being predicted to be highest at intermediate competitor densities and reduced at higher and lower densities, producing a dome shaped relationship. We investigated the effects of competitor density using male swordtails, which form dominance hierarchies and have already been demonstrated to defend a food resource. We found that both aggression (F_2,32 = 5.392; P = 0.010) and time at a food resource (F_2,32 = 3.574; P = 0.040) vary with differences in competitor density, and that the frequency of aggression significantly predicts time at the food resource only at an intermediate density (P = 0.033; r²adj = 0.219). The ability to vary the level of defence with respect to the immediate environment may result in fitness benefits to male swordtails. Further studies examining changes in behaviour over time and examining interacting influencing factors would be beneficial.     

Replicate divergence between and within sounds in a marine fish: the copper rockfish (Sebastes caurinus)

Understanding the factors that influence larval dispersal and connectivity among marine populations is critical to the conservation and sustainable management of marine resources. We assessed genetic subdivision among ten populations of copper rockfish (Sebastes caurinus) representing paired samples of outer coast and the heads of inlets in five replicate sounds on the west coast of Vancouver Island, British Columbia, using 17 microsatellite DNA loci. Overall, subdivision (F_ST) was low (F_ST = 0.031, P < 0.001), but consistently higher between paired coast and head of inlet sites (mean F_ST = 0.047, P < 0.001) compared to among the five coast sites (mean F_ST = ?0.001, P > 0.5) or among the five head of inlet sites (mean F_ST = 0.026, P < 0.001). Heterozygosity, allelic richness and estimates of effective population size were also lower in head of inlet sites than in coast sites. Bayesian analysis identified two genetic groups across all samples, a single genetic group among only coast samples, two genetic groups among head of inlet samples and two genetic groups within each sound analysed separately. Head of inlet copper rockfish tended to be shorter with lower condition factors and grew more slowly than coast sites fish. Reduced physical connectivity and selection against immigrants in contrasting outer coast–head of inlet environments likely contribute to the evolution of population structure of copper rockfish. Based on genetic connectivity, coast sites appear to be better served by existing marine protected areas than are head of inlet sites.     

Evaluation of the causality of the low‐density lipoprotein receptor gene (LDLR) for serum lipids in pigs

A significant quantitative trait locus (QTL) for low‐density lipoprotein cholesterol (LDL‐C) and total cholesterol (TC) was identified around the LDLR gene on chromosome 2 (SSC2) in a White Duroc × Erhualian F₂ resource population and Sutai pigs in our previous study. However, in previous reports, the causality of LDLR with serum lipids is controversial in pigs. To systematically assess the causality of LDLR with serum lipids, association analyses were successively performed in three populations: Sutai pigs, a White Duroc × Erhualian F₂ resource population and a Duroc × (Landrace × Large White) population. We first performed a haplotype‐based association study with 60K SNP genotyping data and evidenced the significant association with LDL‐C and TC around the LDLR gene region. We also found that there is more than one QTL for LDL‐C and TC on SSC2. Then, we evaluated the causalities of two missense mutations, c.1812C>T and c.1520A>G, with LDL‐C and TC. We revealed that the c.1812C>T SNP showed the strongest association with LDL‐C (P = 5.40 × 10^?11) and TC (P = 3.64 × 10^?8) and explained all the QTL effect in Sutai pigs. Haplotype analysis found that two missense SNPs locate within a 1.93‐Mb haplotype block. One major haplotype showed the strongest significant association with LDL‐C (P = 4.62 × 10^?18) and TC (P = 1.06 × 10^?9). However, the c.1812C>T SNP was not identified in the White Duroc × Erhualian intercross, and the association of c.1520A>G with both LDL‐C and TC did not achieve significance in this F₂ population, suggesting population heterogeneity. Both missense mutations were identified in the Duroc × (Landrace × Large White) population and showed significant associations with LDL‐C and TC. Our data give evidence that the LDLR gene should be a candidate causative gene for LDL‐C and TC in pigs, but heterogeneity exists in different populations.     

Male aggressiveness in a polygynous ungulate varies with social and ecological context

Aggression is a social behaviour which can be affected by numerous factors. The quality and quantity of food resources may play an important role in the aggressiveness of territorial ungulates as the defence of these resources influences female choice and mating opportunities. However, the relationship between food resources and aggression remains poorly understood. We assessed the ecological and social factors that influence aggression in Lama guanicoe, a territorial ungulate exhibiting resource‐defence polygyny, during three periods (group‐formation, mating and post‐mating) in the reproductive seasons of 2014 and 2016. We recorded 460 focal observations of territorial (family groups, solitary) and non‐territorial (mixed and bachelor groups) males. We performed analyses at the population level (including all focal observations) and at the group level (each social unit separately), to test whether the factors that influence aggression differ at these different scales. We also identified proxies of vegetation quality as potential predictors of aggression. At the population level, we found that the presence of aggressive behaviour peaked during the mating season and that post‐mating aggression may have been driven by inter‐annual environmental variations. For family groups and solitary males, variables reflecting high vegetation quality/quantity were predictors of aggressive behaviour, reflecting the resource‐defence strategy of this species. Conversely, for mixed‐group males, aggression may be more associated with social instability and group size, although this hypothesis has yet to be tested. Our research reinforces the idea that aggression can occur in multiple contexts depending on male status (e.g. territorial or non‐territorial) and contributes to our understanding of how ecological (i.e. availability of food resources) and social factors influence aggression in a territorial ungulate.     

Reproductive biology of Chinese minnow Hemiculterella sauvagei Warpachowski, 1888 in the Chishui River,China

This study describes the reproductive biology of the Chinese minnow Hemiculterella sauvagei. The length‐weight relationship, sex ratio, spawning season, size at first maturity, and fecundity were analyzed based on 685 specimens collected from the Chishui River between July 2011 and July 2012. The relationship between standard length (SL) and body weight (BW) were estimated as BW = 2.14 × 10^?4 × SL^2.801 (R² = 0.839; N = 413; P < 0.05) for females and BW = 1.31 × 10^?4 × SL^3.001 (R² = 0.868; N = 272; P < 0.05) for males. The female to male sex ratio, 1.52 : 1, differed significantly from a 1 : 1 ratio. Females predominated in standard lengths >12 cm. Analyses of the monthly variation in the gonadosomatic index (GSI), the monthly proportions of macroscopic gonadal maturity, and the size distribution of oocytes consistently suggested a prolonged spawning season of H. sauvagei from March to August, with a peak from April to May. Logistic curves describing the relationship between proportion of maturity (P_r) at each length interval and standard length were estimated as P_r = 1/(1 + e^{26.867–0.306SL}) (R² = 0.999; N = 413; P < 0.05) for females and P_r = 1/(1 + e^{10.522–0.142SL}) (R² = 0.999; N = 272; P < 0.05) for males. Size at first maturity was estimated as 7.4 cm for males and 8.8 cm SL for females. Absolute fecundity varied from 563 to 5052, with a mean of 2413 ± 874 oocytes per ovary. The relative fecundity was estimated to be 41–299, with a mean of 171 ± 55 oocytes per ovary. The present study provides useful information for fishery management and resources conservation.     

The Pillars of Hercules as a bathymetric barrier to gene flow promoting isolation in a global deep‐sea shark (Centroscymnus coelolepis)

Knowledge of the mechanisms limiting connectivity and gene flow in deep‐sea ecosystems is scarce, especially for deep‐sea sharks. The Portuguese dogfish (Centroscymnus coelolepis) is a globally distributed and near threatened deep‐sea shark. C. coelolepis population structure was studied using 11 nuclear microsatellite markers and a 497‐bp fragment from the mtDNA control region. High levels of genetic homogeneity across the Atlantic (Φ_ST = ?0.0091, F_ST = 0.0024, P > 0.05) were found suggesting one large population unit at this basin. The low levels of genetic divergence between Atlantic and Australia (Φ_ST = 0.0744, P < 0.01; F_ST = 0.0015, P > 0.05) further suggested that this species may be able to maintain some degree of genetic connectivity even across ocean basins. In contrast, sharks from the Mediterranean Sea exhibited marked genetic differentiation from all other localities studied (Φ_ST = 0.3808, F_ST = 0.1149, P < 0.001). This finding suggests that the shallow depth of the Strait of Gibraltar acts as a barrier to dispersal and that isolation and genetic drift may have had an important role shaping the Mediterranean shark population over time. Analyses of life history traits allowed the direct comparison among regions providing a complete characterization of this shark's populations. Sharks from the Mediterranean had markedly smaller adult body size and size at maturity compared to Atlantic and Pacific individuals. Together, these results suggest the existence of an isolated and unique population of C. coelolepis inhabiting the Mediterranean that most likely became separated from the Atlantic in the late Pleistocene.     

Mitochondrial DNA phylogeography of Spodoptera exigua across a broad geographic area in China

The beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), is an important agriculture pest in China that causes serious economic losses in some of the main crop‐producing areas. To monitor and manage this pest effectively, it is necessary to investigate its phylogeographic patterns in China. In this study, we used a partial sequence of mitochondrial DNA Cytb gene consisting of 724 bps to investigate the genetic diversity of the beet armyworm. A total of 765 individuals from 47 populations across the main distribution range of the species were collected, and 112 haplotypes were identified. Moderate‐to‐high levels of genetic diversity (Hd = 0.672 ± 0.017, Pi = 0.00268 ± 0.00021) for the total populations were obtained. Phylogenetic and median‐joining network analyses indicated there was no distinct geographic distribution pattern among haplotypes. Overall, the study also revealed significant differentiation among some populations (P < 0.05). The F_ST values of Shenyang population (SY2012–SY 2014), as well as Baoding (BD), Taian (TA), Lucheng (LC), Zhengzhou (ZZ) and Wuhan (WH), were significantly different from those of the populations in most other locations. Hierarchical AMOVA showed there was no significantly genetic structure between populations located in seven geographic regions and four main bioclimatic zones. Finally, unimodal mismatch distribution combined with negative Tajima's D (D = ?2.696, P < 0.001) and Fu's F_S (F_S = ?207.228, P > 0.05) indicated recent population expansion of S. exigua at large spatial scales in China.     

Fine-scale genetic population structure in a mobile marine mammal: inshore bottlenose dolphins in Moreton Bay, Australia

Highly mobile marine species in areas with no obvious geographic barriers are expected to show low levels of genetic differentiation. However, small‐scale variation in habitat may lead to resource polymorphisms and drive local differentiation by adaptive divergence. Using nuclear microsatellite genotyping at 20 loci, and mitochondrial control region sequencing, we investigated fine‐scale population structuring of inshore bottlenose dolphins (Tursiops aduncus) inhabiting a range of habitats in and around Moreton Bay, Australia. Bayesian structure analysis identified two genetic clusters within Moreton Bay, with evidence of admixture between them (F_ST = 0.05, P = 0.001). There was only weak isolation by distance but one cluster of dolphins was more likely to be found in shallow southern areas and the other in the deeper waters of the central northern bay. In further analysis removing admixed individuals, southern dolphins appeared genetically restricted with lower levels of variation (AR = 3.252, π = 0.003) and high mean relatedness (r = 0.239) between individuals. In contrast, northern dolphins were more diverse (AR = 4.850, π = 0.009) and were mixing with a group of dolphins outside the bay (microsatellite‐based STRUCTURE analysis), which appears to have historically been distinct from the bay dolphins (mtDNA Φ_ST = 0.272, P < 0.001). This study demonstrates the ability of genetic techniques to expose fine‐scale patterns of population structure and explore their origins and mechanisms. A complex variety of inter‐related factors including local habitat variation, differential resource use, social behaviour and learning, and anthropogenic disturbances are likely to have played a role in driving fine‐scale population structure among bottlenose dolphins in Moreton Bay.     

Reduced resource defence in an uncertain world: an experimental test using captive nutmeg mannikins

Recent models of economic defence in a group-foraging context predict that the frequency of aggressive interactions should decline as resource density increases, but empirical studies have provided only equivocal support for this prediction. We suggest that whether or not foragers have information concerning the location of patches will influence both the intensity of aggressive encounters and the effect that changes in food density will have on aggression. The intensity of aggression should be greatest when patch locations are known to all, making resources spatially predictable and the availability of alternatives more certain. When food is hidden, increasing the density of patches should have little effect on aggression levels, mostly as a result of the greater uncertainty about the availability of replacement food patches. To test these predictions, we investigated the effect of patch density on the use of aggressive behaviour in nutmeg mannikins, Lonchura punctulata, when food patches were either visible (signalled patch location) or hidden (unsignalled patch location) to all foragers. As predicted, we found that the intensity of aggressive encounters was higher when patch location was signalled than when it was not. Moreover, the effect of patch density on aggression depended on whether patch location was signalled or not. When patch location was unknown, the number of aggressive encounters was unaffected by changes in patch density, but when food location was signalled, increasing patch density resulted in the expected decline in the frequency of aggression.     

Diet composition,feed preferences and mouth morphology of early stage silver therapon (Leiopotherapon plumbeus,Kner 1864) larvae reared in outdoor tanks

This study examined the diet composition, feeding preferences, and mouth morphology of the silver therapon (Leiopotherapon plumbeus, Kner 1864) larvae under captive conditions. Larvae were reared in outdoor tanks (4 m³) with natural food grown 2 weeks prior to start of larval rearing. Food preference was measured by the Chesson's electivity index (α_i). Gut content analysis of larvae sampled between 5 and 25 days after hatching (DAH) showed the dominance in the diet by zooplankton, mainly copepod nauplii, cladocerans and insect larvae. Small fish larvae (5–9 DAH; 3.32–6.29 mm standard length) preferred cladocerans, ciliates and copepod nauplii; whereas older larvae (12–25 DAH; 5.45–19.26 mm standard length) preferred insect larvae over cladocerans and adult insects. The mouth gape size at 5 DAH was 359 μm and increased to 3.75 mm at 40 DAH when body size grew at an average rate of 0.59 mm d^?1. The standard length (SL) of L. plumbeus larvae was strongly associated with mouth size (r² = 0.98, P < 0.05), indicating a progressive increase of ingested prey size of the fish larvae. These results clarified the early life feeding ecology of this species, which is essential in developing effective hatchery techniques.     

Aggressive and Foraging Behavioral Interactions Among Ruffe

The ruffe, Gymnocephalus cernuus, is a nonindigenous percid in the Great Lakes. Ruffe are aggressive benthivores and forage over soft substrates. Laboratory studies in pools (100cm diameter, 15cm water depth) were conducted to determine whether fish density (low=2, medium=4, high=6 ruffe per pool) changed foraging and aggressive behaviors with a limited food supply of chironomid larvae. All fish densities demonstrated a hierarchy based on aggressive interactions, but ruffe were most aggressive at low and high fish densities. Time spent in foraging was lowest at the low fish density. The best forager at the low fish density was the most aggressive individual, but the second most aggressive fish at the medium and high fish density was the best forager and also the one chased most frequently. A medium fish density offered the best energetic benefits to ruffe by providing the lowest ratio of time spent in aggression to that spent foraging. Based on our results, ruffe should grow best at an intermediate density. With high ruffe densities, we would also expect disparity in size as the more aggressive fish are able to garner a disproportionate amount of the resources. Alternatively, as the Great Lakes are a fairly open system, ruffe could migrate out of one area to colonize another as populations exceed optimal densities.     

Using blood plasma cortisol concentration and fish behaviour to determine temperature avoidance in the estuarine‐dependent fish species Rhabdosargus holubi (Steindachner, 1881) (Sparidae)

In order to test the hypothesis that a combination of blood cortisol measurements and behavioural observations can be used to estimate the avoidance temperature of the estuarine‐dependent Cape stumpnose, Rhabdosargus holubi (Steindachner, 1881) (Sparidae), fish were kept at increasing water temperatures at a rate of 3°C d^?1 over 7 days. Plasma cortisol concentrations were significantly influenced by the interaction of time and treatment (F = 10.9, P < 0.01) with cortisol concentrations in fish kept at increasing temperature averaging 293 ng ml^?1 on day 7. This was 5.4 times higher than the average value for control fish (29 ng ml^?1). For the first 6 days, average cortisol concentration of control fish was 25.7 ± 5.0 ng ml^?1, while values for fish from the temperature treatment ranged from 8.3 to 176.6 ng ng ml^?1. These values combined with behaviour observations suggest that cortisol concentration and behavioural changes may be used to detect both a low and an acute stress response.     

Evaluation of optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel,Anguilla japonica

The study aimed at evaluating the optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel, Anguilla japonica, as assessed by fish growth performance and fish body composition. Five semi‐purified experimental diets were formulated to contain 0 (TA₁), 15 (TA₁₇), 30 (TA₃₂), 60 (TA₆₂) and 120 (TA₁₁₉ mg TA kg^?1 diet on a dry matter (DM) basis in the form of DL‐α‐tocopheryl acetate (TA). After a 4‐week conditioning period, fish (15 ± 0.3 g) were randomly distributed into aquaria in groups of 20 at 25 ± 1.0°C (mean ± SD). One of the five diets was fed on a DM basis to fish in three randomly selected aquaria twice daily to satiation (approximately 3% of wet body weight per day at the beginning and 2% of wet body weight per day at the end of the feeding trial) for 12 weeks. At the end of the 12‐week feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) were determined; these were significantly lower in control fish than in fish fed supplemented diets (P < 0.05). The values for fish fed TA₁₇ were significantly higher than for fish fed TA₁, TA₆₂ or TA₁₁₉ (P < 0.05). There were no significant differences in WG, FE or PER among fish that were fed TA₁₇ and TA₃₂, among those that were fed TA₃₂ and TA₆₂, and among those that were fed TA₆₂ and TA₁₁₉ (P > 0.05). There were also no significant differences in SGR among fish fed TA₃₂, TA₆₂ or TA₁₁₉ (P > 0.05). A broken‐line regression analysis on the basis of WG, SGR, FE and PER showed that dietary vitamin E requirements of juvenile eels were 21.2, 21.6, 21.2 and 21.5 (mg kg^?1 diet), respectively. These results indicate that the dietary vitamin E requirement could be <21.2 mg kg^?1 but <21.6 mg kg^?1 diet in juvenile eel, A. japonica, when DL‐α‐tocopheryl acetate is used as the dietary vitamin E source.     

Influence of feeding the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) on the non-specific cellular and humoral defence mechanisms of rainbow trout (Oncorhynchus mykiss)

Previous studies have shown that leucine metabolite β‐hydroxy‐β‐methylbutyrate (HMB) increases the immune function in animals as measured by cellular and humoral immune responses. In the present study the influence of feeding HMB on the nonspecific cellular and humoral defence mechanisms and protection against furunculosis in rainbow trout (Oncorhynchus mykiss) was examined. HMB was fed in a pelleted ration at either 0 (control), 10, 25 or 50 mg  kg^?1 bw day^?1 for 8 weeks. Blood and pronephros cells were taken at random from 10 fish in each group for the analyses. The respiratory burst activity (RBA) and potential killing activity (PKA) of phagocytes, lymphocyte proliferation stimulated by either concanavalin (ConA) or lipopolysaccharide (LPS), lysozyme activities and total immunoglobulin (Ig) levels in plasma were analysed at 0, 1, 2, 3, 4, 6 and 8 weeks. After 4 weeks of feeding HMB, a challenge test was performed by injection of Aeromonas salmonicida into the fish. HMB approximately doubled the respiratory burst activity and potential killing activity ability of polymorphonuclear (PMN) and morphonuclear (MN) cells (P < 0.01) and increased the mitogen‐stimulated lymphocyte proliferation (P < 0.01) when compared with the control group. HMB feeding also increased (P < 0.01) the lysozyme activity in plasma and total Ig levels in serum. During the 14‐day challenge test, mortality was decreased (P < 0.01) by up to 62% in HMB‐fed fish compared with the control group mortality. In conclusion, the non‐specific immune enhancement by HMB resulted in protection against furunculosis in the rainbow trout.     

Population statistics of the migratory hilsa shad,Tenualosa ilisha,in Sindh,Pakistan

In order to estimate the population dynamics of the hilsa shad, Tenualosa ilisha, fishery in Sindh, the key population parameters of growth, mortalities, recruitment pattern, exploitation and maximum sustainable yield are discussed. Length frequency data were collected from April to October 2004 from the main commercial (hilsa) landings at Thatta, Sindh. Estimated parameters of the von Bertalanffy (Hum. Biol. 10, 181–213) growth model were L_∞ = 31.5 cm, K = 1.5 year^?1, t₀ = ?0.10 year as obtained by the electronic length frequency analysis (ELEFAN I). Estimated natural, fishing, and total mortalities were 2.21, 0.673, 2.89 year^?1, respectively. The relative biomass per recruit (B′/R) was 0.95 and yield per recruit (Y′/R) was 0.06 using the knife‐edge selection. The exploitation ratio at the maximum sustainable yield (MSY) was E_max = 1.0 year^?1, fishing mortality at MSY was F_max = 2.89 year^?1, average target F_opt = 0.5 year^?1 and F_limit = 1.47 year^?1. The catch and effort data from 1981 to 2004 (MFD, Karachi) were analyzed using the catch and effort data analysis (CEDA) computer programme. Estimated biological reference point of MSY for the Fox model was 891 tonnes (t), R² = 0.75; for the Schaefer and Pella‐Tomlinson models MSY = 744 t, R² = 0.49, the outputs of which appeared to be more conservative than the Fox model which indicated a better fit. The overall situation of hilsa fishery is in severe stress and appears vulnerable to overexploitation. On the basis of the present findings, serious attention is required to provide appropriate access of the fish to the Indus River during the spawning period as well as to impose a ban on fishing during upstream migration and on undersized catch to prevent this traditional fishery in this area.     

Ionregulation in juvenile swordspine snook (Centropomus ensiferus,Poey, 1860) in relation to environmental salinity

Ninety‐nine swordspine snook Centropomus ensiferus (9.80 ± 0.3 g, mean ± SE) were studied in order to evaluate the influence of salinity on physiological properties under rearing conditions. Growth performance, survival rates, and ion concentrations (Na⁺, K⁺, Cl^?) as well proximal composition were measured over 76 days. Fish were exposed to three experimental salinities (0, 10, 20 ‰ , three replicates per treatment) and maintained in plastic tanks with a recirculation system equipped with flow‐through aquaria pumps (533 L per tank). Fish were fed twice daily to apparent satiation; at the end of the experiment the weight of fish kept in 10 ‰ was higher than that of fish kept in 0 and 20 ‰ , however no significant differences (P > 0.05) were observed among the experimental salinities. Survival was significantly lower in 10 ‰ salinity than in fish kept in 20 and 0 ‰ salinities. No significant differences (P > 0.05) were found in the Condition factor (K), specific growth rate (SGR), or in plasma Na⁺, K⁺, or Cl^? concentrations among treatments. Salinities also did not affect body composition (P > 0.05), but were significantly lower (P < 0.05) than at the start of the experiment. However, towards the end of the experiment a large accumulation of visceral fat in fish farmed in the three salinities (VFI > 4%) was observed. Water quality was within the optimum range (T: 28.7 ± 0.1°C; O2: 5.6 ± 0.1 mg L^?1; ammonia: 0.2 mg L^?1) for the growth of swordspine snook. Data indicates that C. ensiferus is an ionoregulator fish and able to cultivate successfully in various osmotic conditions, and in turn, maintain high levels of survival in captivity.     

The effects of productivity and seasonality on life history: comparing age at maturity among moose (Alces alces) populations

The productivity hypothesis in respect of an animal species’ geographical range predicts that whereas higher productivity at the equatorial periphery of a species’ range favours superior competitors, lower productivity at the centre of a species’ range favours high reproduction and reduced competitive traits. I test whether life‐history patterns follow this hypothesis, using demographic data from 15 Canadian moose (Alces alces) populations. Two models are contrasted; the first assumes that intraspecific variation in age at maturity is explained proximately by density and juvenile mortality. Age at maturity was found to increase with decreasing juvenile mortality (P = 0.01) and increasing density (P = 0.006). To test the productivity hypothesis, the second model additionally included primary productivity and seasonality as geographical explanatory variables that would ultimately influence age at maturity via juvenile mortality and density. Path analysis indicated that including productivity and seasonality improved the model predictions of variation in age at maturity (R_a² 0.56 and 0.85). In bivariate comparisons, seasonality was negatively associated (P = 0.01) with age at maturity. In the best model, however, primary productivity was the environmental variable that explained 25% of the variance in age at maturity, and forest cover replaced seasonality as an explanatory variable. The positive association between primary productivity and age at maturity is consistent with the productivity hypothesis. Relative to populations that lived at the centre of the species’ range (51°N), moose populations living in relatively high productivity and low seasonality environments (equatorial periphery of species’ range; 48°N) experienced less juvenile mortality, more variable year‐to‐year density, higher relative density and slower life history (slower growth rate, later age at maturity, lower fecundity).     

Aggression,interference, and the functional response of coral-feeding butterflyfishes

Functional responses describing how foraging rates change with respect to resource density are central to our understanding of interspecific interactions. Competitive interactions are an important determinant of foraging rates; however, the relationship between the exploitation and interference components of competition has received little empirical or theoretical consideration. Moreover, little is known about the relationship between aggressive behavioural interactions and interference competition. Using a natural gradient of consumer and resource densities, we empirically examine how aggressiveness relates to consumer–consumer encounter rates and foraging for four species of Chaetodon reef fish spanning a range of dietary niche breadths. The probability of aggression was most strongly associated with both total consumer and resource densities. In contrast, total encounter rates were best predicted by conspecific consumer density, and were highest for the most specialised consumer (Chaetodon trifascialis), not the most aggressive (Chaetodon baronessa). The most specialised consumer, not the most aggressive, also exhibited the largest reduction in foraging rates with increasing consumer density. Our results support the idea of a positive link between the exploitation and interference components of competition for the most specialised consumer. Moreover, our results caution against inferring the presence of ecological interactions (competition) from observations of behaviour (aggression and agonism) alone.     

Rise and fall of a wolf population: genetic diversity and structure during recovery,rapid expansion and drastic decline

The grey wolves (Canis lupus) of Finland have had a varied history, with a period of rapid population expansion after the mid‐1990s followed by a decline with a current census size of about 140 wolves. Here, we investigate the impact of unstable population size and connectivity on genetic diversity and structure in a long‐term genetic study of 298 Finnish wolves born in 1995–2009 and genotyped for 17 microsatellite loci. During the initial recovery and prior to population expansion, genetic diversity was high (1995–1997: LD‐N_e = 67.2; H_o = 0.749; H_e = 0.709) despite a small census size and low number of breeders (N_c < 100; N_b < 10) likely reflecting the status of the Russian source population. Surprisingly, observed heterozygosity decreased significantly during the study period (t = ?2.643, P = 0.021) despite population expansion, likely a result of an increase in inbreeding (F_IS = 0.108 in 2007–2009) owing to a low degree of connectivity with adjacent Russian wolf population (m = 0.016–0.090; F_ST = 0.086, P < 0.001) and population crash after 2006. However, population growth had a temporary positive impact on N_e and number of family lines. This study shows that even strong population growth alone might not be adequate to retain genetic diversity, especially when accompanied with low amount of subsequent gene flow and population decline.     

Genetically distinct populations of northern shrimp,Pandalus borealis,in the North Atlantic: adaptation to different temperatures as an isolation factor

The large‐scale population genetic structure of northern shrimp, Pandalus borealis, was investigated over the species’ range in the North Atlantic, identifying multiple genetically distinct groups. Genetic divergence among sample localities varied among 10 microsatellite loci (range: F_ST = ?0.0002 to 0.0475) with a highly significant average (F_ST = 0.0149; P < 0.0001). In contrast, little or no genetic differences were observed among temporal replicates from the same localities (F_ST = 0.0004; P = 0.33). Spatial genetic patterns were compared to geographic distances, patterns of larval drift obtained through oceanographic modelling, and temperature differences, within a multiple linear regression framework. The best‐fit model included all three factors and explained approximately 29% of all spatial genetic divergence. However, geographic distance and larval drift alone had only minor effects (2.5–4.7%) on large‐scale genetic differentiation patterns, whereas bottom temperature differences explained most (26%). Larval drift was found to promote genetic homogeneity in parts of the study area with strong currents, but appeared ineffective across large temperature gradients. These findings highlight the breakdown of gene flow in a species with a long pelagic larval phase (up to 3 months) and indicate a role for local adaptation to temperature conditions in promoting evolutionary diversification and speciation in the marine environment.