Mark C. Belk

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• PhD
• Professor at Brigham Young University

Over the past decades, stable isotopes have been infrequently used to characterise host-parasite trophic relationships. This is because we have not yet identified consistent patterns in stable isotope values between parasites and their host tissues across species, which are crucial for understanding host-parasite dynamics. To address this, we initi...

Species delimitation can be based on the consideration of several different criteria, including the differentiation of ecological or functional traits. Two species of Pacific rockfish, the dark rockfish (Sebastes ciliatus) and the dusky rockfish (Sebastes variabilis), appear to represent recently divergent evolutionary lineages. We evaluate evidenc...

Investigating fundamental processes in biology requires the ability to ground broad questions in species‐specific natural history. This is particularly true in the study of behavior because an organism's experience of the environment will influence the expression of behavior and the opportunity for selection. Here, we provide a review of the natura...

Sablefish (Anoplopoma fimbria, Anoplopomatidae) and shortraker rockfish (Sebastes borealis, Sebastidae) co-occur in deepwater marine habitats in the northeast Pacific. Both species are economically valuable, but their ecologies are not well known. We used stable isotope analysis of carbon and nitrogen to explore isotopic niches of A. fimbria and S....

Evolutionary fitness is determined by how an organism allocates energy, or other limited resources, to reproduction during its lifetime. For iteroparous organisms, two alternative patterns of lifetime reproductive allocation are terminal investment and reproductive restraint. Terminal investment maximizes an individual’s current reproductive output...

Heterochrony—alteration to the rate or timing of development—is an important mechanism of trait differentiation associated with speciation. Heterochrony may explain the morphological divergence between two polyploid species, June sucker (Chasmistes liorus) and Utah sucker (Catostomus ardens). The larvae of both species have terminal mouths; however...

Feeding morphology permits animals to adapt to changing environments and is often under strong selection. We evaluated if bill shape varies according to differences in dietary prey taken across geographical ranges (North America, Central America, South America, and Caribbean islands) in a ubiquitous, New World raptor species, the American kestrel (...

Livebearing fishes are a common model for studying the effects of predation on prey biology. Numerous studies have found differences in life history, sexual selection, behavior, and morphology between populations of the same species that co‐occur with predators and those that do not. Alfaro cultratus is a livebearing fish with populations in differ...

We characterise the complete mitochondrial genomes (mitogenomes) of Black rockfish ( Sebastes melanops Girard, 1856; n = 1), Dark rockfish ( Sebastes ciliatus Tilesius, 1813; n = 2) and Dusky rockfish ( Sebastes variabilis Pallas, 1814; n = 2). The lengths of the mitogenomes are 16,405 bp for S. melanops , 16,400 bp for both S. ciliatus and 16,400...

Quagga mussels (Dreissena bugensis) are considered one of the most deleterious invasive species in freshwater ecosystems because they can alter food webs by changing energy and nutrient flows. Generally, the predicted effect of quagga mussels on the trophic niche of co-occurring fish is a decrease in trophic level and a shift to use of more littora...

We report the complete mitochondrial genomes of two rockfish: Sebastes maliger and Sebastes norvegicus. The mitogenomes consist of 13 protein-coding regions, 22 tRNAs, two rRNAs, and one control region. Sebastes mitogenome control regions are highly variable due to the presence of repeat sequences. The mitogenomes for S. maliger and S. norvegicus a...

Rockfish (genus Sebastes) assemblages can inform mechanisms of coexistence and maintenance of diversity in ecological communities. Coexistence theory characterizes ecological assemblages as following either a deterministic niche differentiation model, or a stochastic lottery model. We used natural abundances of carbon and nitrogen stable isotopes f...

Climate change projections in the western United States suggest that snowpack levels and winter precipitation will decline, but mean annual precipitation levels will remain unchanged. Mountain streams that once saw a constant source of water from snowpack will begin to see large seasonal variation in flow. Increased stream intermittency will create...

The relationship between June sucker (Chasmistes liorus, Jordan, 1878) and Utah sucker (Catostomus ardens, Jordan & Gilbert, 1881) has been a matter of controversy since the mid 1900s. Chasmistes liorus is endemic to Utah Lake, UT and has a subterminal mouth adapted for pelagic feeding. Catostomus ardens is widely distributed throughout the Bonnevi...

Data on age and growth of fishes is critical for effective management; however, growth rates documented in one location may not be representative of other locations, especially for species that occur across wide geographic ranges. Sebastes maliger, quillback rockfish, occur across a broad latitudinal range, but their growth patterns have been quant...

Invasive species can cause disruption of the trophic niche of resident species such that patterns of energy flow through ecological systems are altered. Quagga mussel Dreissena rostriformis bugensis Andrusov, 1897, a notorious invasive species, was introduced to Lake Powell (Utah and Arizona, USA) in 2012 and colonized the entire reservoir by 2017....

The cost of reproduction hypothesis suggests that allocation to current reproduction constrains future reproduction. How organisms accrue reproductive costs and allocate energy across their lifetime may differ among species adapted to different resource types. We test this by comparing lifetime reproductive output, patterns of reproductive allocati...

For fishes, swimming performance is an important predictor of habitat use and a critical measure for the design of effective fish passage systems. Few studies have examined burst and prolonged types of swimming performance among several co-occurring species, and swimming performance in many fish communities is undocumented. In this study, we charac...

Distribution and abundance of common parasitic nematodes in marine fishes is not well documented in many geographic regions. Understanding the influence of large-scale environmental changes on infection rates of fish by nematodes requires quantitative assessments of parasite abundance for multiple host species. We collected samples of two species o...

Multigenerational effects (often called maternal effects) are components of the offspring phenotype that result from the parental phenotype and the parental environment as opposed to heritable genetic effects. Multigenerational effects are widespread in nature and are often studied because of their potentially important effects on offspring traits....

Communal breeding is a reproductive system in which more than a single pair of individuals share parental care duties. Burying beetles (genus Nicrophorus) breed on small vertebrate carcasses, which is used as a food source for their young. On larger carcasses, burying beetles will breed communally, forming multiple male-female associations. A signi...

Body and head shape among fishes both vary between environments influenced by water velocity and across ontogeny. Although the shape changes associated with variation in average water velocity and ontogeny are well documented, few studies have tested for the interaction between these two variables (i.e., does ontogenetic shape variation differ betw...

Predation is known to have a significant effect on life history diversification in a variety of species. However, physical constraints of body shape and size can sometimes limit life history divergence. We test this idea in the Costa Rican livebearing fish Alfaro cultratus. Individuals in this species have a narrow body and keeled ventral surface,...

Life-history traits are directly linked to fitness, and therefore, can be highly adaptive. Livebearers have been used as models for understanding the evolution of life histories due to their wide diversity in these traits. Several different selective pressures, including population density, predation, and resource levels, can shape life-history tra...

The morphologies of craters on planetary surfaces reveal clues about the geologic mechanisms by which they originate and subsequently evolve, as well as the materials and physical variables inherent to the environment in which they formed. We carried out a quantitative multivariate analysis of shape descriptors derived from the outlines of craters...

Predation is ubiquitous in nature and can be an important component of both ecological and evolutionary interactions. One of the most striking features of predators is how often they cause evolutionary diversification in natural systems. Here, we review several ways that this can occur, exploring empirical evidence and suggesting promising areas fo...

Resource allocation to growth, reproduction, and body maintenance varies within species along latitudinal gradients. Two hypotheses explaining this variation are local adaptation and counter‐gradient variation. The local adaptation hypothesis proposes that populations are adapted to local environmental conditions and are therefore less adapted to e...

Body and head shape in fish responds to environmental factors such as water flow rate, food sources, and niche availability. However, the way in which fish respond to these environmental factors varies. In Central Chile, multiple river and lake systems along the coast provide an ideal study site to investigate these types of shape changes. We use g...

A central problem in evolutionary biology is to determine whether adaptive phenotypic variation within species (microevolution) ultimately gives rise to new species (macroevolution). Predation environment can select for trait divergence among populations within species. The implied hypothesis is that the selection resulting from predation environme...

Rationale Differences in stable isotope composition between an animal and its diet are quantified by experimentally derived diet‐tissue discrimination factors. Appropriate discrimination factors between consumers and prey are essential for interpreting stable isotope patterns in ecological studies. While available for many taxa, these values are ra...

Competition has long been recognized as a central force in shaping evolution, particularly through character displacement. Yet research on character displacement is biased, as it has focused almost exclusively on pairs of interacting species while ignoring multispecies interactions. Communities are seldom so simple that only pairs of species intera...

June sucker (Chasmistes liorus) is a long-lived, endangered fish endemic to Utah Lake, Utah. For several decades June sucker have failed to recruit sufficient numbers to the adult size classes such that the current wild population consists of a small number of old adults and it continues to decline. Vital rates of June sucker are influenced by clim...

Culverts can provide a significant barrier to fish passage by fragmenting fish habitats and impeding the passage success of small-bodied fish. Geographical connectivity is critical to the maintenance of diverse fish assemblages. Culverts with high cross-sectional velocity can cause population fragmentation by impeding passage of small, freshwater f...

In this study, we considered potential causes of variation in testis size in the livebearing fish Brachyrhaphis rhabdophora. We evaluated variation in testes mass among individual males and among populations that occupy different selective environments. First, we predicted that small males should allocate more to testes mass than large males (i.e.,...

Background Assemblages of fishes in lakes and reservoirs in the western USA are dominated by non-native, large-bodied, piscivorous fishes that lack a shared evolutionary history. Top predators in these crowded systems are often characterized by unstable population dynamics and poor somatic growth rates. One such assemblage is in Fish Lake, located...

Background Reservoir communities in the intermountain west are typically dominated by a mix of introduced fishes. Due to the non-coevolved interactions present in these communities, energy flow and trophic interactions may not facilitate optimal growth and survival for all species. It is difficult to predict how well each species will survive in su...

Juvenile survival and growth are critical determinants of evolutionary fitness in most organisms. However, specific effects of population density and habitat quality on survival and growth of larvae vary widely among amphibian species. The Columbia spotted frog (Rana luteiventris), like many amphibians in the arid western United States, is a specie...

Body size generally has an important relationship with fitness, whereby larger body size leads to an increase in fitness through competition, reproductive output and survivorship. However, the traits through which body size increases fitness often differ between the sexes. We tested for the effects of body size on fitness in both sexes using three...

We document movement patterns and home range of Diplomystes camposensis, an endemic and threatened freshwater catfish from Chile. We tracked the movements of seven individuals of different body size (13.5 to 19 cm SL) using portable radio telemetry equipment to investigate movement patterns in relation to day/night activity and habitat use in the S...

Body size generally has an important relationship with fitness, whereby larger body size leads to an increase in fitness through competition, reproductive output and survivorship. However, the traits through which body size increases fitness often differ between the sexes. We tested for the effects of body size on fitness in both sexes using three...

We tested whether brood parasitism could be successful between two co-occurring species of burying beetles, Nicrophorus guttula and Nicrophorus marginatus , and whether these species exhibit an adaptive response to brood parasitism by detecting and removing parasites. We cross-fostered larvae between broods of the two species and created mixed-spec...

In species that require parental care, each parent can either care for their offspring or leave them in the care of the other parent. For each parent this creates three possible parental care strategies: biparental care, uniparental (male or female) care, and uniparental desertion by either the male or female. The burying beetle, Nicrophorus orbico...

Predator density, refuge availability, and body size of prey can all affect the mortality rate of prey. We assume that more predators will lead to an increase in prey mortality rate, but behavioral interactions between predators and prey, and availability of refuge, may lead to nonlinear effects of increased number of predators on prey mortality ra...

Evolution typically occurs in response to a suite of selective pressures. Yet, many studies of natural selection in the wild only investigate a single selective agent at a time. This can be problematic when selective agents act in non- additive ways. Here we evaluate the interactive effects of diet and predation on the evolution of body shape in th...

Behavioral traits of individuals are important phenotypes that potentially interact with many other traits, an understanding of which may illuminate the evolutionary forces affecting populations and species. Among the five axes of temperament is the propensity to behave boldly in the presence of a perceived risk. To determine the effect of differen...

Lake Powell (Colorado River drainage, Utah and Arizona, USA) is an important and unique fishery comprising several nonnative fishes. There are no previous studies of the parasites of the fishes of Lake Powell. We provide a general survey of the metazoan parasites found in the numerically dominant fish species of the reservoir. We collected and surv...

Parasite communities of stream fish assemblages in the western United States are poorly known. We investigated the intestinal parasites of an assemblage of stream fishes in Spanish Fork River in central Utah, USA. Two species, mottled sculpin (Cottus bairdii) and redside shiner (Richardsonius balteatus), had no observable parasites. In the other 3...

Movement of organisms is an important activity that has ecological and evolutionary implications, including individual reproductive success and survival, population growth and persistence, local adaptation, and gene flow. Expression of movement behavior has traditionally been termed dispersal and measured relative to home ranges. This simplistic ap...

Integrative taxonomy (IT) is becoming a preferred approach to delimiting species boundaries by including different empirical criteria. IT methods can be divided into two types of procedures both of which use multiple kinds of evidence: step-by-step approaches test hypotheses by sequential evaluation in a hypothetic-deductive framework, while model-...

June sucker, Chasmistes liorus , is an endangered lake sucker endemic to Utah Lake, Utah, USA. Over the last two decades, captive-raised June suckers have been stocked into Utah Lake to augment the wild population. However, it has become apparent that the fish stocked from captive stock may not always represent the typical June sucker morphology. T...

In species that provide parental care, offspring survival is often completely dependent on protection and resources afforded by the parents. Therefore, parents gain no fitness unless they raise offspring to a critical point of independence. In these species, selection should shape parental life history to increase their chances of surviving to this...

Molecular genetic data suggest that June sucker (Chasmistes liorus) is only shallowly diverged from the co-occurring but phenotypically distinct Utah sucker (Catostomus ardens) in Utah Lake. Phenotypes representing both extreme morphologies (June sucker and Utah sucker) are observed in the small wild population, but relatively large numbers of inte...

Restoration of altered or degraded habitats is often a key component in the conservation plan of native aquatic species, but introduced species may influence the response of the native community to restoration. Recent habitat restoration of the middle section of the Provo River in central Utah, USA, provided an opportunity to evaluate the effect of...

Organisms are selected to maximize lifetime reproductive success by balancing the costs of current reproduction with costs to future survival and fecundity. Males and females typically face different reproductive costs, which makes comparisons of their reproductive strategies difficult. Burying beetles provide a unique system that allows us to comp...

To date, there have been nearly 100 papers published on metazoan parasites of Antarctic fishes, but there has not yet been any compilation of a species list of fish parasites for this large geographic area. Herein, we provide a list of all documented occurrences of monogenean, cestode, digenean, acanthocephalan, nematode, and hirudinean parasites o...

We used genomic and bioinformatic techniques to identify single nucleotide polymorphisms (SNPs) for use in population genetic studies and conservation efforts of North American burying beetles. Genomic reduction, barcoding, 454-pyrosequencing and de novo assembly of the resultant reads yielded 30,399 large contigs (>400 bp) for us to scrutinize. We...

The cyprinid fish Gila atraria Girard (Utah chub) is generally considered a sexually monomorphic species. However, prior observations revealed variation in pelvic fin length within populations that appears sexually dimorphic. We measured the relative pelvic fin length of 419 sexually mature Utah chub from 8 different locations to determine the magn...

Predator community composition can alter habitat quality for prey by changing the strength and direction of consumptive effects. Whether predator community composition also alters prey density via nonconsumptive effects during habitat selection is not well known, but is important for understanding how changes to predator communities will alter prey...

Negotiation models of biparental care predict that parents should partially compensate for a reduction in the level of care that their partner provides. A number of studies, mostly with monogamous birds, have tested this prediction by removing or manipulating the level of effort of one parent and then measuring the response of the other parent. In...

The cost of reproduction hypothesis suggests that current reproduction has inherent tradeoffs with future reproduction. These tradeoffs can be both in the form of energy allocated to current offspring as opposed to somatic maintenance and future reproduction (allocation costs), or as an increase in mortality as a result of morphological or physiolo...

The cost of reproduction theory posits that there are trade-offs between current and future reproduction because resources that are allocated to current offspring cannot be used for future reproductive opportunities. Two adaptive reproductive strategies have been hypothesized to offset the costs of reproduction and maximize lifetime fitness. The te...

Evolution of fish body shapes in flowing and non-flowing waters have been examined for several species. Flowing water can select for fish body shapes that increase steady swimming efficiency, whereas non-flowing water can favor shapes that increase unsteady swimming efficiency. Benthic stream fishes often use areas near the substrate that exhibit r...

The cost of reproduction hypothesis predicts that the level of reproductive investment to current reproduction is constrained by an individual's future reproductive potential or residual reproductive value. Therefore, age, or differences between young and old individuals in residual reproductive value, is expected to influence reproductive investme...

Ecological and environmental gradients create varying selective pressures on organisms that result in differences in optimal life history tactics. Moreover, life histories are inherently multivariate, consisting of a coordinated suite of life history traits that vary over an organism's lifetime. Such variation can be described as a trajectory of ph...

We examined the multivariate life-history trajectories of age 0 and age 1 female Gambusia affinis to determine relative effects of age-based and environment-based cues on reproductive investment. Age 0 females decreased reproductive investment prior to the onset of fall and winter months, while age 1 females increased reproductive investment as the...

Variation in trophic position can be caused by structural changes in food webs that may affect the presence of, or be affected by the presence of, individual species. We examined variation in the trophic position of fishes across 14 stream sites in the Bear River drainage, WY, USA. This drainage is the focus of ongoing conservation of northern leat...

Natural selection often results in profound differences in body shape among populations from divergent selective environments. Predation is a well-studied driver of divergence, with predators having a strong effect on the evolution of prey body shape, especially for traits related to escape behavior. Comparative studies, both at the population leve...

Galaxias platei is widespread and common in southern South America, but its ecology is poorly documented relative to other native species, especially those of commercial importance. Galaxias platei occurs across a large range of environmental conditions, including hydrologically isolated, high-elevation lakes. Consequently, there were several lakes...

Intraspecific morphological variation in fish is typically associated with sexual dimorphism, or one of three common environmental gradients: variation in intensity of predation, variation in water velocity, or variation in feeding niche. The preponderance of examples of environment-associated morphological variation within fish species has been do...

Objective: Some information is available about the parasite fauna and incidence for Clarias gariepinus in Turkey, but digenean parasites have received little attention. The purpose of the study is to contribute to the parasite fauna of Turkey. Methods: From 2007 to 2008, a total 63 Clarias gariepinus that were caught in the Asi River were purcha...

Variation in somatic growth rates is of great interest to biologists because of the relationship between growth and other fitness-determining traits, and it results from both genetic and environmentally induced variation (i.e. plasticity). Theoretical predictions suggest that mean somatic growth rates and the shape of the reaction norm for growth c...

Background / Purpose: Ecological models fit two basic purposes: prediction and explanation. But statistical (empirical) models of nature typically incorporate multivariate terms. We explore dimensionality reduction methods that support one or both model purposes. Main conclusion: Partial least squares regression (PLSR) incorporates dimensional...

Background/Question/Methods Life-history theory predicts that where energy is limited, there exists a trade-off in which an organism must invest a limited quantity of energy either toward growth in size or toward storage for maintenance and survival. Natural selection will determine which strategy is favored. Burying beetles Nicrophorus orbicollis...

Background/Question/Methods In organisms that express bi-parental care, both males and females can incur costs associated with reproduction. Nicrophorus orbicollis is a burying beetle that serves as a model organism for studying life history and resource allocation. We evaluate the influence that male experience and age has on bi-parental reprodu...

Background/Question/Methods We assess the cost of reproduction hypothesis using the burying beetle Nicrophorus orbicollis as a model organism looking at differences across latitudes to determine if reduction in the length of the reproductive season associated with increasing latitude have resulted in genetically based changes in life history strate...

Background/Question/Methods Burying beetles are excellent model organisms for studying life history traits because of their unique biology (biparental care on a discrete resource) and their ease of manipulation in both the laboratory and field settings. Many species of burying beetles coexist and face potential competitive interactions as they at...

Background/Question/Methods Species that coexist and use similar resources often partition resource use along at least some niche axes to minimize competition and maintain coexistence. Species may differ in times of activity, food characteristics, breeding periods, or habitat use. Two species of burying beetle (Nicrophorus guttula and N. marginat...

Models of habitat selection often assume that organisms choose habitats based on their intrinsic quality, regardless of the position of these habitats relative to low-quality habitats in the landscape. We created a habitat matrix in which high-quality (predator-free) aquatic habitat patches were positioned adjacent to (predator-associated) or isola...

Predation can cause morphological divergence among populations, while ontogeny and sex often determine much of morphological diversity among individuals. We used geometric morphometrics to characterize body shape in the livebearing fish Brachyrhaphis rhabdophora to test for interactions between these three major shape-determining factors. We assess...

Current culvert design standards for fish passage compare sustained swimming abilities of the target fish species with a cross sectional area based average flow velocity through the culvert. Such policies dictate relatively large culvert barrels and do not recognize the significant role of reduced velocity zones in the culvert near boundaries. Test...

Native fishes worldwide have declined as a consequence of habitat loss and degradation and in-troduction of non-native species. In response to these declines, river restoration projects have been initiated to enhance habitat and remove introduced fishes; how-ever, non-native fish removal is not always logistically feasible or socially acceptable. C...

It is often assumed that indicator species can act as surrogates for conservation of other taxa because the habitat characteristics that limit the distribution of indicators should also affect multiple co-occurring native species. However, this assumption is rarely explicitly tested. Here, we test whether four fish species are potential indicators...

The process of dispersal is determined by the interaction of individual (intrinsic) traits and environmental (extrinsic) factors. Although many studies address and quantify dispersal, few evaluate both intrinsic and extrinsic factors jointly. We test the relative importance of intrinsic traits (exploration tendency and size) and extrinsic factors (...

The process of dispersal is determined by the interaction of individual (intrinsic) traits and environmental (extrinsic) factors. Although many studies address and quantify dispersal, few evaluate both intrinsic and extrinsic factors jointly. We test the relative importance of intrinsic traits (exploration tendency and size) and extrinsic factors (...

The endangered June sucker, Chasmistes liorus, is a long-lived, zooplanktivorous sucker endemic to Utah Lake, Utah. Habitat degradation both in the tributaries, where adults spawn, and in the lake has contributed to near complete mortality of larval and juvenile fish within the first few weeks after hatching, leading to a long-term lack of recruitm...

One of the fundamental determinants of survival and growth of individuals is population density. Typically, individuals exhibit negative density dependence, but positive density dependence (Allee effect) may occur. Understanding patterns of density dependence is important for conservation and management of species that have low densities as a resul...

Lake suckers of the genus Chasmistes are a unique and important component of the fish assemblages of the western USA. To review recent research, discuss issues, and exchange information, researchers and managers working on the various species participated in a symposium on lake sucker biology as part of the 2010 annual meeting of the Western Divisi...