Mark-recapture Techniques Research Articles

Movement and growth of the coral reef holothuroids Bohadschia argus and Thelenota ananas

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 551:201-214 (2016) - DOI: https://doi.org/10.3354/meps11720 Movement and growth of the coral reef holothuroids Bohadschia argus and Thelenota ananas Steven W. Purcell1,2,*, Toby P. Piddocke2, Steven J. Dalton1,2, You-Gan Wang3 1Marine Ecology Research Centre, Southern Cross University, Military Road, East Lismore, NSW 2480, Australia 2National Marine Science Centre, Southern Cross University, Charlesworth Bay, Coffs Harbour, NSW 2450, Australia 3School of Mathematical Sciences, Queensland University of Technology, Brisbane, QLD 4000, Australia *Corresponding author: steven.w.purcell@gmail.com ABSTRACT: Tropical sea cucumbers are among the largest mobile invertebrates on coral reefs and are widely regarded as sedentary. Mark-recapture methods provide empirical estimates of movement and growth but have often been unsuccessful with sea cucumbers. We applied a new photographic mark-recapture technique to measure rates of short-term displacement (over a few days), long-term displacement (over 2 yr) and growth of Bohadschia argus and Thelenota ananas on the Great Barrier Reef, Australia. Recapture rates were 50–100% in the short-term study and 50–77% in the long-term study. In the short-term studies in 2010 and 2012, average movement rates ranged 2–8 m d-1 for B. argus and 5–9 m d-1 for T. ananas. Long-term movement averaged 15–47 m over 2 yr, with some individuals displacing less than 5 m and several others moving more than 100 m. Our study shows that some tropical sea cucumbers can be highly mobile, and many appear to display home ranging. Growth rates were positive yet modest for smaller individuals, but many of the large individuals lost weight over the 2 yr study. Classical growth models indicated that B. argus attain an average maximum size in 15–20 yr, and the empirical data on growth show that they can lose or gain weight thereafter. Hence, longevity appears to be at least several decades. The 2 species are slow growing, and the negative growth in large individuals undermines previous estimates of growth and longevity based on size-frequency data. KEY WORDS: Sea cucumber · Displacement · Behaviour · Echinoderm · Photographic identification · Mark-recapture · Marine invertebrate Full text in pdf format Supplementary material PreviousNextCite this article as: Purcell SW, Piddocke TP, Dalton SJ, Wang YG (2016) Movement and growth of the coral reef holothuroids Bohadschia argus and Thelenota ananas. Mar Ecol Prog Ser 551:201-214. https://doi.org/10.3354/meps11720 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 551. Online publication date: June 09, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

A comparison of reproductive patterns and adult dispersal in sympatric introduced and native marine crabs: implications for species characteristics of invaders

The introduction and translocation of nonindigenous marine species is widespread and can pose severe threats to biodiversity and ecosystem functioning. Predicting which species are potential invaders is of particular interest to ecologists. One approach is to identify characteristics that predispose a species to becoming a successful invader. Since its introduction in the 1980’s, the invasive Asian shore crab, Hemigrapsus sanguineus, has shown a remarkable ability to colonize rocky intertidal habitats along the east coast of the United States. In Long Island Sound H. sanguineus occurs sympatrically with the functionally equivalent, but non-invasive, native Atlantic mud crab, Panopeus herbstii. The presence of both species at the same site allowed us to make a detailed, simultaneous assessment of life history traits and adult dispersibility of co-occurring invading and native crab species. We investigated fecundity and maturation rates, length of breeding season and brood production for both species, and conducted field experiments using mark–recapture techniques to determine mobility patterns. Our results show that the nonindigenous Asian crab has a greater reproductive potential than the native mud crab as evidenced by a longer breeding season, multiple brood production and higher fecundity rates. Field experiments confirmed previous studies indicating H. sanguineus is a highly mobile crab, and further demonstrated that adult Asian crabs are more likely than mud crabs to disperse from their shelter/refuge sites. Recovery rates for native mud crabs were significantly higher than those for Asian crabs in three experimental trials, across sites and years. This work provides new information about life history characteristics of both species and supports the hypothesis that high reproductive potential combined with high adult dispersal ability may be important factors associated with the invasion/establishment success of the Asian shore crab. More study is needed, however, to determine the applicability of these findings to other highly successful marine invaders.

Life History and Demographic Characteristics of the Magdalena River Turtle (Podocnemis lewyana): Implications for Management

We conducted a four-year study of the life history parameters of the endangered freshwater turtle Podocnemis lewyana (Testudines: Podocnemididae) in four channels connecting wetlands to the Magdalena River in northern Colombia. Using capture–mark–recapture techniques, we documented body size growth rates, sex ratios, and size class distributions, and estimated survival rates for juveniles and adults. We also used body size/clutch size and body size/track width correlations to estimate the body sizes of females that nested in beaches in the Magdalena River near the study sites. The body size at first nesting (30 cm straight-line carapace length) was comparable to the estimate obtained by inspecting the reproductive tracts of 70 females using a sonograph. Growth rate analyses showed adult males to be smaller than adult females with an estimated size at sexual maturity of 20 cm straight-line carapace length. Females begin nesting at 5–6 years of age and may lay up to four clutches annually with a mean clutch...

Climate and density influence annual survival and movement in a migratory songbird.

Assessing the drivers of survival across the annual cycle is important for understanding when and how population limitation occurs in migratory animals. Density-dependent population regulation can occur during breeding and nonbreeding periods, and large-scale climate cycles can also affect survival throughout the annual cycle via their effects on local weather and vegetation productivity. Most studies of survival use mark-recapture techniques to estimate apparent survival, but true survival rates remain obscured due to unknown rates of permanent emigration. This is especially problematic when assessing annual survival of migratory birds, whose movement between breeding attempts, or breeding dispersal, can be substantial. We used a multistate approach to examine drivers of annual survival and one component of breeding dispersal (habitat-specific movements) in a population of American redstarts (Setophaga ruticilla) over 11years in two adjacent habitat types. Annual survival displayed a curvilinear relation to the Southern Oscillation Index, with lower survival during La Niña and El Niño conditions. Although redstart density had no impact on survival, habitat-specific density influenced local movements between habitat types, with redstarts being less likely to disperse from their previous year's breeding habitat as density within that habitat increased. This finding was strongest in males and may be explained by conspecific attraction influencing settlement decisions. Survival was lowest in young males, but movement was highest in this group, indicating that apparent survival rates were likely biased low due to permanent emigration. Our findings demonstrate the utility of examining breeding dispersal in mark-recapture studies and complement recent work using spatially explicit models of dispersal probability to obtain greater accuracy in survival estimates.

An indirect method for assessing the abundance of introduced pest Myocastor coypus (Rodentia) in agricultural landscapes

AbstractPest management requires the development of robust monitoring tools. In Italy, coypu Myocastor coypus (nutria) have been controlled since the early 1990s, but the effectiveness of these measures has never been tested. With the aim of developing a reliable and volunteer‐based method for the long‐term monitoring of coypu abundance in agricultural landscapes, we calibrated an index based on surveys for coypu paths against density estimates obtained through a standardized mark–recapture technique. Two trapping sessions were performed in winter for each of 12 1‐km long stretches of irrigation canals and watercourses using 15 baited cage traps. Trapping sessions lasted 7 days each, with a 10‐day break between sessions. Population size was assessed using three methods: Peterson–Lincoln's formula, capwire estimators and accumulation curves. Active coypu paths and five habitat variables were recorded by walking on the edge of both banks. The variables were then related to population size (y) by means of multi‐regressive models, testing for the predictive power of the selected models by leave‐one‐out cross‐validation. Multi‐regressive models included only the number of coypu paths with the best performances achieved by the model based on Peterson–Lincoln formula, supporting path count as an effective method to assess the abundance of the coypu in agricultural landscapes. Concurrently, to assess the field suitability of the indirect method, surveys for coypu paths were carried out on 122 randomly chosen 3‐km long stretches of irrigation canals and watercourses in the central part of the River Po valley (c. 15 000 km2; N Italy). The highest (>8/100 m) mean number of paths was recorded in the central part of the study area. According to the regression models, the overall number of coypu is predicted to range between 350 000 and 1 100 000, raising doubts about the effectiveness of current control measures.

APHIS: A new software for photo-matching in ecological studies

Unique body characteristics are increasingly used for individual recognition to avoid the effort and the potential negative effects of capture–mark–recapture technique. As a consequence there is a growing demand for computer procedures to assist users in photo-recognition of an individual. We present a new software for photo-matching developed to minimize the pre-processing time and maximize the speed of the matching procedure. In APHIS photos can be processed in batches of hundreds and users can select between two alternative matching procedures, one interactive, built as an extension of existing and freely available software, and one automatic. We assessed its performance in terms of individual recognition and time efficiency and illustrate its use with real capture-photo–recapture studies on a reptile and an amphibian species, the Balearic Lizard Podiarcis lilfordi and the Northern spectacled salamander Salamandrina perspicillata, with contrasting skin patterns.

Using Genetic Markers as Individual Tags: a Case Study of a Mark–Recapture Estimate of Adult Muskellunge Population Size

AbstractTag retention, tag reporting rate, misreading of tags, and other issues are common concerns with traditional tagging methods when marking fish for various stock assessments. These concerns have prompted the development and evaluation of alternative marking techniques by fisheries scientists. Wildlife scientists have overcome these obstacles by using genetic samples in lieu of tagging when studying rare, elusive, and capture‐sensitive species. Recent technological advances facilitate similar alternatives for fisheries stock assessment. Muskellunge Esox masquinongy populations exist at low density and are difficult to sample; the Muskellunge is therefore an appropriate species to use in assessing this tool. We used microsatellite DNA analysis of samples from two connected lakes in north‐central Minnesota to estimate adult population size using mark–recapture techniques. In total, 178 unique fish were identified during a trap‐net marking period; 59 individuals were identified within an electrofishing resampling period, and 28 of those were recaptures, recognized by their matching genotypes. Based on these data, we obtained a population estimate of 369 adults (95% confidence interval = 269–470). The results of this study demonstrate the utility of genetic markers in place of traditional tagging methods for fish.Received September 24, 2014; accepted December 1, 2014

First evidence of potadromy and partial migration in black basses: shoal bass Micropterus cataractae (Actinopterygii, Centrarchidae) in the Upper Flint River, USA

Potamodromy, migration for reproduction within freshwater systems, is widely practiced among fishes, but has rarely been reported for Micropterus spp. Recent evidence has shown that shoal bass (M. cataractae; Williams & Burgess, 1999) in the upper Flint River, USA, undergo migrations during the spawning season to large shoal complexes; however, the magnitude and prevalence of these migrations are unknown. To test the hypothesis that these fish exhibit potadromy, 376 shoal bass were tagged with anchor tags over a four-year period. Each spring, shoal bass migrated up to 200 km to reach spawning areas in the piedmont, and these migrations appeared to be more common in fish living in the coastal plain area of the river. Fish from the piedmont area moved less, likely due to proximity of spawning habitat. Results of this study have suggested that shoal bass are highly migratory in connected systems, traveling long distances to spawn in specific areas. Thus, the scope of shoal bass management and conservation has broadened considerably. Other Micropterus species dwelling in lotic habitats may exhibit similar migratory patterns in their native and/or introduced ranges, and this possibility could be examined using mark-recapture techniques similar to those used in this study.

Rodent population and community responses to forest-based biofuel production

Intensively managed forests in the southeastern United States are a potential source of cellulosic bioenergy and, as conversion technologies improve and demand increases, a greater land area may be required to produce biofuel feedstocks. However, responses of wildlife to forest-based biofuel production are largely unknown. We examined the 4-year response of rodent populations and assemblages to a range of biofuel production regimes, including harvesting residual woody debris and intercropping switchgrass (Panicum virgatum), in an intensively managed loblolly pine (Pinus taeda) forest in eastern North Carolina, USA. We investigated abundance, demography, and community response of rodents in a randomized and replicated field experiment using mark-recapture techniques during 2009–2012. Whereas removal of downed woody biomass did not affect abundance, diversity, or demography of rodents, we detected species-specific effects of incorporating switchgrass. After switchgrass was well established, invasive house mice (Mus musculus) were most abundant in plots with switchgrass. In contrast, white-footed mice (Peromyscus leucopus) were commonly captured in plots without switchgrass and other rodents were not affected by biofuel treatments. Across the study, natural succession exerted greater effects on rodent species and the rodent community than biofuel production regimes. As remaining logs and stumps decay and become limiting, downed wood may become more important to rodents. Our results indicate that intercropping switchgrass and harvesting residual woody material had limited effects on rodents in the Coastal Plain of North Carolina, USA within 4 years of stand establishment.

Replicated origin of female-biased adult sex ratio in introduced populations of the trinidadian guppy (Poecilia reticulata).

There are many theoretical and empirical studies explaining variation in offspring sex ratio but relatively few that explain variation in adult sex ratio. Adult sex ratios are important because biased sex ratios can be a driver of sexual selection and will reduce effective population size, affecting population persistence and shapes how populations respond to natural selection. Previous work on guppies (Poecilia reticulata) gives mixed results, usually showing a female-biased adult sex ratio. However, a detailed analysis showed that this bias varied dramatically throughout a year and with no consistent sex bias. We used a mark-recapture approach to examine the origin and consistency of female-biased sex ratio in four replicated introductions. We show that female-biased sex ratio arises predictably and is a consequence of higher male mortality and longer female life spans with little effect of offspring sex ratio. Inconsistencies with previous studies are likely due to sampling methods and sampling design, which should be less of an issue with mark-recapture techniques. Together with other long-term mark-recapture studies, our study suggests that bias in offspring sex ratio rarely contributes to adult sex ratio in vertebrates. Rather, sex differences in adult survival rates and longevity determine vertebrate adult sex ratio.

Spatio-temporal distribution patterns of three stream-dwelling freshwater mussel species: towards a strategy for representative surveys

Conservation efforts for freshwater mussels (Unionoida) require a priori assessments of their populations’ status quo. Unfortunately, collection of representative census and other data for most European species is currently hampered by an insufficient understanding of inter- and intra-specific variation in distribution patterns. We assessed distribution and movement in three Unio crassus populations and one sympatric population of Anodonta anatina and Unio pictorum, respectively. We surveyed vertical movement across four sediment depths, and horizontal movement by mark-recapture technique in 3-month intervals. For all the populations, movement and the proportion inhabiting surface layers increased considerably from winter to spring/summer. Spatial aggregation levels remained stable for some populations, while others became increasingly randomly distributed during the study. One U. crassus population exhibited elevated mortality and displayed movement rates exceeding twice those of conspecific populations. The visible proportion of U. crassus populations differed by up to 69% between sites. Current monitoring guidelines in Europe often insufficiently account for the extensive inter- and intra-specific differences in spatio-temporal distribution patterns observed. We suggest developing internationally standardised protocols that specify sampling season and methodology. In particular, U. crassus surveys should be restricted to summer months, and hand-sampling is crucial for some populations.

Application of the Genetic Mark–Recapture Technique for Run Size Estimation of Yukon River Chinook Salmon

AbstractWe present an application of the genetic mark–recapture technique to estimate salmon run size in a large river. Application of this technique requires modifications to estimation methodology. Under a typical Lincoln–Petersen mark–recapture estimation of salmon run size (N = M/p), individual fish are captured and marked (M) in the lower river and are recaptured (m) at escapement (E: the number of fish reached spawning ground) monitoring sites selected upriver where the proportion of marked individuals (p = m/E) is estimated. In this genetic mark–recapture technique, the marked individuals are not captured and recaptured, but rather the naturally distinctive genetic (marked) population is captured and recaptured. Genetically, the lower river population is a mixture of multiple genetic stocks, whereas the upriver escapement population consists of a single genetic stock. Hence, the mark–recapture experiment (N = M/pm) is reversed. The proportion of “marked” genetic stock (pm) is estimated in the lower river, and size of the “marked” stock in the lower river (M) is estimated by summing its upriver escapement (Em) and harvest (Cm) between the lower and upper portions of river (M = Em+Cm). The harvest is calculated as a product of total upriver harvest (C) and the proportion of the “marked” stock (pcm) in the harvest (Cm = C·pcm). Further, when the proportion of multiple genetic stocks (pk) is identified, stock‐specific run size (Nk = N·pk), escapement (Ek = Nk−Ck, where Ck = C ·pck), and exploitation rate (Exk = Ck /Nk) can also be estimated, which provides substantially more information than does the conventional approach. We illustrate an application of this technique for estimating run size of Chinook Salmon Oncorhynchus tshawytscha in the Yukon River, Alaska.Received June 6, 2013; accepted November 20, 2013

Common species affects the utility of non-invasive genetic monitoring of a cryptic endangered mammal: The bridled nailtail wallaby

Non-invasive methods of monitoring wild populations (such as genotyping faeces or hair) are now widely used and advocated. The potential advantages of such methods over traditional direct monitoring (such as live capture) are that accuracy improves because sampling of non-trappable individuals may be possible, species in difficult and remote terrain can be surveyed more efficiently, and disturbance to animals is minimal. Few studies have assessed the effects of interactions between species on remote sampling success. We test the use of non-invasive monitoring for the cryptic, forest-dwelling, solitary and endangered bridled nailtail wallaby (Onychogalea fraenata) that is sympatric with the ecologically similar and more common black-striped wallaby (Macropus dorsalis). Six types of hair traps were tested for 3668 trap days, and hairs were caught with about a 10% success rate. Camera traps showed that baited hair traps targeted both wallaby species. We microscopically identified hair as bridled nailtail wallaby or black-striped wallaby. We compared these hairs and their genotypes (using seven microsatellite loci) with known bridled nailtail wallaby hairs and genotypes derived from animal trapping. Trapped bridled nailtail wallaby hairs had characteristics that could be mistaken for black-stripe wallaby hairs; characteristics were not diagnostic. Genetic assignment tests consistently differentiated the known bridled nailtail wallaby samples from identified black-striped wallaby samples, however genetic overlap between most of the microsatellite markers means that they are not suitable for species identification of single samples, with the possible exception of the microsatellite locus B151. With similar trapping effort and within the same area, live-capture mark-recapture techniques estimated 40-60 individuals and non-invasive methods only detected 14 genotypes. A species-specific genetic marker would allow more efficient targeting of bridled nailtail wallaby samples and increase capture rates.

NATURAL HISTORY OF DEKAY’S BROWNSNAKE, STORERIA DEKAYI (HOLBROOK, 1836), AT A SITE IN NORTHWESTERN PENNSYLVANIA

A population of Dekay’s Brownsnake, Storeria dekayi was studied using mark-recapture techniques in Erie County, Pennsylvania, USA during the spring, summer and autumn of 2012. Morphometric data were similar to that reported for the species, with adult females averaging larger and more massive than adult males. However, sexual dimorphism in snout-vent length (SVL) and total length (TL) was not significantly different (P>0.05) in juveniles, although relative tail length (tl/TL) was dimorphic. Relative tail length in both juveniles and adults was greater in males (tl/TL = 0.22-0.27) than females (tl/TL = 0.18-0.23). Storeria dekayi were active from 21 March through 22 October, and displayed a bimodal activity pattern, with peaks in April and August. Using the Schnabel and the Schumacher-Eschmeyer methods, population size was estimated to be 122 ± 19 and 130 ± 35 individuals, respectively. Density was estimated to be 244 and 260 snakes/ha, and biomass 1.60 and 1.71 kg/ha. Additional data regarding population structure, mortality, diet, reproduction, body temperature, movements and site fidelity are also presented.

Assessment of an immunomarking technique for the study of dispersal of Culicoides biting midges

Capture–mark–recapture techniques are used to determine the dispersal and survival of arthropods, including vector groups such as Culicoides. An assumption of these studies is that capture and the subsequent marking process does not impact of the survival and behaviour of the marked individual. The small size of Culicoides means that a significant mortality and disruption of normal behaviour such as host-location can be caused by the process of collection. Here we evaluate a technique, novel to the study of dispersal in vectors, to mark Culicoides directly and indirectly without prior capture. The acquisition and subsequent detection of marker protein by Culicoides exposed to a treated substrate was investigated in the laboratory. The technique was then assessed in a small-scale field trial where a defined section of resting habitat was sprayed with an egg white solution and Culicoides caught within the vicinity were tested for the presence of egg protein. It was found that up to 100% of Culicoides acquired the protein marker in the laboratory with no apparent impact on survival. In the field, pools of Culicoides obsoletus collected next to the treated area were found to be positive for the protein, suggesting that the technique could be used in larger-scale studies. The definition of a behaviourally non-invasive technique for marking Culicoides will greatly increase our understanding of the natural dispersal behaviour of Culicoides and other vectors.

Use by small mammals of a chronosequence of tropical rainforest revegetation

Context The conversion of tropical rainforest to grazing pasture results in a drastic change in small-mammal community composition. Restoring the landscape through ecological revegetation is thus an increasingly important management technique to conserve rainforest mammals. Aims This study aimed to determine the habitat ages at which species of small mammals recolonised revegetated habitats on the southern Atherton Tablelands, north-eastern Queensland, Australia. We focussed on changes in rainforest mammal abundance and diversity with increasing habitat age. Methods Small-mammal trapping and mark–recapture techniques investigated mammal diversity, abundance and community composition within remnant rainforest, three age classes of ecological revegetation and abandoned grazing pasture. Key results Small-mammal community composition differed between remnant rainforest and abandoned grazing pasture. The pasture and 3-year old revegetated sites were similar in composition, both lacking rainforest small mammals. Six- and 7-year old revegetation plantings provided suboptimal habitat for both rainforest and grassland mammals, whereas 16- and 22-year old revegetated habitats were dominated by rainforest species, with some individuals being frequently recaptured. Conclusions As revegetated habitats aged, the small-mammal community composition transitioned from a grassland-like composition to a community dominated by rainforest species. Implications Although rainforest small mammals were very occasionally captured within the 6- and 7-year old habitats, revegetated plantings were not dominated by rainforest species until the habitat was 16 years old. This highlights the importance of commencing revegetation as early as possible to minimise future population declines and maximise the conservation of rainforest mammals.

Delayed life history effects, multilevel selection, and evolutionary trade‐offs in the California tiger salamander

Delayed life history effects (DLHEs) occur when fitness in one life stage affects fitness in subsequent life stages. Given their biphasic life cycle, pond-breeding amphibians provide a natural system for studying DLHEs, although these effects are not restricted to species with biphasic life histories. In this study, we used multiple mark-recapture techniques enabled by a large trapping array to monitor components of fitness and resulting DLHEs in a population of the endangered California tiger salamander (Ambystoma californiense). We found that DLHEs are prominent across all life stage transitions and that there is variation in whether selection acts primarily at the individual or cohort level. We also demonstrated that there is more than an order of magnitude variation in mean cohort fitness, providing tremendous variation for DLHEs to act upon. We documented an evolutionary trade-off between mass at emergence and date of emergence, which may play a role in maintaining the variation in mass (fitness) at emergence. A literature review revealed that such high levels of intercohort variation occur in many other pond-breeding amphibians, and that appropriately documenting the magnitude of intercohort variation requires long-term studies (roughly two population turnovers). Given the profound effect that DLHEs can have on population dynamics, quantifying intercohort variation in mean fitness and the level(s) at which selection acts will be very important for developing accurate models of population dynamics. In general, when developing models of population dynamics, more attention should be paid to variation in mean fitness and not just variation in total numbers.

Life history of the Marbled Whiptail Lizard Aspidoscelis marmorata from the central Chihuahuan Desert, Mexico

The life history of a population of marbled whiptail lizard, Aspidoscelis marmorata , was examined from 1989 to 1994 in the sand dunes of the Biosphere Reserve of Mapimi, in Northern Mexico. Lizards were studied using mark-recapture techniques. Reproduction in females occurred between May and August, with birth hatchlings matching the wet season in August. Reproductive activity was highest in the early wet season (July). Males and females reached adult size class at an average age of 1.7 years and 1.8 years, respectively. Body size of males attained an asymptote around 90 mm snout-vent length and females around 82 mm snout-vent length, at an age of approximately 3.6 years and 3.0 years, respectively. The density varied from 7 to 85 individuals / 1.0 ha. The Mexican population had late maturity, relatively long life expectancy, and fewer offspring. Overall, the observed data for A. marmorata and the expectations of life history theory for a late maturing species (K - rate selection) are in agreement.

Parallelism Isn’t Perfect: Could Disease and Flooding Drive a Life-History Anomaly in Trinidadian Guppies?

Nonparallel evolution, where independent populations occupy similar environments but show phenotypic differences, can uncover previously ignored selective factors. We investigated a nonparallelism in the life-history strategy of a Trinidadian guppy population, a system famous for parallel adaptation to differences in predation risk. We tested the hypothesis that high mortality drives an observed fast life-history pattern (i.e., earlier maturation and more frequent reproductive events) that is atypical for a low-predation environment. Using mark-recapture techniques, we compared neighboring low-predation populations, finding significantly higher mortality rates in the population with atypical life-history traits. Mortality was elevated during the wet season, when flooding was common. Moreover, individuals from the anomalous population were more likely to transition from healthy to infected disease states. Our results stand out against previous patterns observed in this system, indicating that higher mortality caused by disease and flooding may have selected for a faster life history. Thus, we highlight that even in systems famous for parallel adaptation, variation in selective pressures can result in nonparallel phenotypic evolution.

Network transmission inference: Host behavior and parasite life cycle make social networks meaningful in disease ecology

The process of disease transmission is determined by the interaction of host susceptibility and exposure to parasite infectious stages. Host behavior is an important determinant of the likelihood of exposure to infectious stages but is difficult to measure and often assumed to be homogenous in models of disease spread. We evaluated the importance of precisely defining host contact when using networks that estimate exposure and predict infection prevalence in a replicated, empirical system. In particular, we hypothesized that infection patterns would be predicted only by a contact network that is defined according to host behavior and parasite life cycle. Two competing host contact criteria were used to construct networks defined by parasite life cycle and social contacts. First, parasite-defined contacts were based on shared space with a time delay corresponding to the environmental development time of nematode parasites with a direct fecal-oral life cycle. Second, social contacts were defined by shared space in the same time period. To quantify the competing networks of exposure and infection, we sampled natural populations of the eastern chipmunk (Tamias striatus) and infection of their gastrointestinal helminth community using replicated longitudinal capture-mark-recapture techniques. We predicted that (1) infection with parasites with direct fecal-oral life cycles would be explained by the time delay contact network, but not the social contact network; (2) infection with parasites with trophic life cycles (via a mobile intermediate host; thus, spatially decoupling transmission from host contact) would not be explained by either contact network. The prevalence of fecal-oral life cycle nematode parasites was strongly correlated to the number and strength of network connections from the parasite-defined network (including the time delay), while the prevalence of trophic life cycle parasites was not correlated with any network metrics. We concluded that incorporating the parasite life cycle, relative to the way that exposure is measured, is key to inferring transmission and can be empirically quantified using network techniques. In addition, appropriately defining and measuring contacts according the life history of the parasite and relevant behaviors of the host is a crucial step in applying network analyses to empirical systems.