Use the filters below to find awards made to CSU students by Program, Campus, or Year.
COAST Award Program
National Audubon Society Conference
Reading a Birds Mind with GIS: Utilizing Technology as a Conservation Tool
Traditional monitoring methods of Endangered Species has always utilized harass by survey methodology that can be distressing to species of interest. However, with today's advances in technology we can redefine and modernize monitoring methods and techniques. By implementing ArcGIS and ArcPro accompaniments like Survey123 and Collector, we can analyze the role that these GIS applications can play in developing predictive models that can guide habitat management. These applications, as well as the utilization of drone technology, can provide more accurate recovery metrics to study the populations of Endangered Species such as the Western Snowy Plover and California Least Tern.
The Joint Meeting of Ichthyologists and Herpetologists
Evaluating the Importance of Reef-Based Resources for Reproduction in a Temperate Reef Fish
California sheephead are among the most ecologically important fish on temperate reefs in California and Mexico, yet little is known about their reproductive ecology. Environmental factors can affect reproductive success in fish populations in a variety of ways, including by affecting diet. The goal of this study was to determine if any differences in reproduction among populations of California sheephead (Semicossyphus pulcher) were related to differences in diets among them. We measured the prey availability, diet composition, and batch fecundity of California sheephead on three large reefs within the Southern California Bight. Reproductive output, diet, and prey availability all differed between years, implying that variation in prey availability affected diet, which affected reproductive output. Understanding how changes to kelp forest habitat impact reproductive output can aid in future management efforts of economically and ecologically important species of fish.
The 7th International Symposium on Deep-Sea Corals
Deep Sea Coral and Sponge Species Distribution Models for Southern California
Deep-sea coral and sponge species (DSCS) are some of the longest-lived marine species and their complex, three-dimensional structure provides habitat for demersal fish and invertebrates. Until recently, the relationship between DSCS and fish species in the Southern California Bight was not fully understood; however, recent work on benthic assemblages in Southern California revealed relationships between several DSCS and demersal fishes. Habitat suitability maps, which predict where these DSCS species may occur, are needed to understand what areas of suitable habitat are currently protected and what areas are still exposed to potential destruction. In this study, we used Generalized Additive Models (GAMs) to identify environmental factors that are the best proxies for predicting DSCS occurrence. We explored seven main categories of environmental variables which have been hypothesized or demonstrated to affect the distribution of DSCS species of interest. These variables include (1) bottom currents using Regional Oceanographic Modeling System, (2) temperature, (4) depth, (5) seafloor slope, (6) surface primary productivity, and (7) dissolved oxygen. All variables were chosen due to their influence on DSCS physical and/or metabolic needs. We then used these models to develop habitat suitability maps for several species of DSCS that were associated with increased occupancy of 26 species of demersal fishes. These maps expand the current knowledge of DSCS distributions in southern California and provide a tool to inform management decisions, such as where to draw boundaries for new areas of conservation and protection.
Joint Meeting of Ichthyologists and Herpetologists
Developmental ontogeny of Giant Sea Bass, Stereolepis gigas
The Giant Sea Bass, Stereolepis gigas, is listed as critically endangered by the IUCN, and is the largest bony fish of the coast of Southern California. After fertilization Giant Sea Bass, larvae develop in the plankton, but little is known about their early life history stages or what mechanisms drive their recruitment. This study aims to examine, in detail the first critical stages of this species including the egg, yolk sac, pre-flexion, flexion, post-flexion, and the transformation stages. I will be imaging the eggs and larvae using Zen software. Once this is completed the fixed larvae will be dehydrated and cartilage will be stained with Alcian Blue. Following the staining of the cartilage the bone will be stained using Alizarin Red. After the staining is complete and skeletal data collected, some specimens will be destained and then preserved. These will be used to analyze neurological development in the future. Knowledge of these developmental stages will give us a better understanding of what is driving Giant Sea Bass larval recruitment, thus allowing better protection of nursery areas and rational fisheries management.
Joint Meeting of Ichthyologists and Herpetologists: American Elasmobranch Society
Habitat characteristics of catshark oviposition sites and potential nursery grounds off central California
Catsharks (Scyliorhinidae) are the most speciose family of extant sharks; however, there is a paucity of information known about their life histories. Three deepsea scyliorhinids occur in the waters off central California; brown (Apristurus brunneus), longnose (Apristurus kampae), and filetail (Parmaturus xaniurus) catsharks. It is necessary to determine essential fish habitat of these scyliorhinid species and their nursery grounds for improved fisheries management as free-living catsharks and catshark egg cases are often incidentally caught as bycatch in commercial fisheries. Therefore, the purpose of this study is to determine and compare spatial and habitat associations of these catsharks’ oviposition locations. Subsequently we can infer locations of nurseries where certain habitat types are used consistently and where egg cases occur in high densities. Archived video of the seafloor collected primarily in Monterey Bay by the Monterey Bay Aquarium Research Institute (MBARI) and the National Marine Fisheries Service, Southwest Fisheries Science Center’s Fishery Ecology Division (NMFS-SWFSC-FED) were used to collect spatial and habitat information and to identify eggcases to species. Video from MBARI and SWFSC showed eggcases were commonly observed at depths between 101-524 m. Video footage has revealed that A. brunneus and P. xaniurus preferentially deposit their eggs within the Monterey Submarine Canyon specifically by wrapping egg case tendrils on sessile invertebrates, rocky outcrops, or derelict fishing gear. Apristurus kampae eggs do not have tendrils and have not yet been observed. Preliminary results indicate that sponges are used preferentially as oviposition sites for both A. brunneus and P. xaniurus.
Effects of beach structure and sediment characterization on meiofaunal diversity along the California coast
Estimates of diversity and the intricate ways in which communities are shaped by their environment have been of interest to science long before the idea of biodiversity was formally acknowledged. Meiofauna represent the polyphyletic group of infaunal microscopic organisms whose body size allows them to pass through a 500μm mesh net but be retained by a 20μm mesh net (Mare 1942). Due to their small size and taxonomic obscurity, they remain a fundamentally understudied group despite their integral position at the base of the sandy-beach food web and close association with the surrounding environs. To study the distribution of meiofaunal communities with respect to community composition, sediment samples were taken along the length of the California coast and analyzed using high-throughput sequencing techniques. Sediment characteristics and beach morphodynamic profiles were analyzed to link differences in community structure to possible abiotic drivers. Ultimately, the results of this study will provide a detailed and unprecedented description of meiofaunal composition and abundance along a highly variable and biodiverse coastline, and allow for the formation of hypotheses specific to meiofauna, which have been classically lumped in with more easily studied macrofauna despite vast differences in biology, life history, and tolerance to environmental stressors.
Eastern Pacific Ocean Conference, Mt. Hood, OR
Benthic microplastic distribution in Humboldt Bay, northern California: a comparative study of surface sediments based on proximity from the shore
Plastic production and use has increased steadily over the last century primarily because of plastic’s resistance to corrosion and low production costs. Plastics enter the marine environment from non-point sources such as rivers, wind, and fishing activities, and point-sources like sewage treatment plants, dumping, and landfills. This research focuses on microplastics (MPs), specifically those within the size range of 0.335 to 5 mm, because of the uptake potential by detrital and filter feeding organisms. Quantifying the amount of MPs in the marine environment is crucial because bioaccumulation of plastics in marine life can affect humans who consume marine organisms. This study compares the concentration of MPs in sediments between the intertidal and subtidal environments of Humboldt Bay, California. We hypothesized that the intertidal samples would have higher MP concentrations due to their proximity to shore and increased anthropogenic activity. Sediment samples were collected using hand corers in the intertidal region and a Smith McIntyre grab in the subtidal region. Organic material in the samples was oxidized using 30% hydrogen peroxide, then a density differentiation technique was used to separate plastics for further microscope identification. Preliminary results show that about 95% of MPs found in sediment are microfibers and the remaining 5% of MPs are degraded hard plastic. To date, more MPs have been found in the subtidal region than the intertidal region, with 980 MP particles recovered in the subtidal region and 340 MP particles recovered in the intertidal region. This study confirms the presence of microplastics within Humboldt Bay, and defines their distribution with proximity to shoreline. These results can be used by the community to update recycling practices, wastewater treatment procedures to mitigate microfibers, and raise awareness about marine life ingestion of plastics.
American Association for the Advancement of Science, Washington, DC
Vascularization of male blue rockfish (Sebastes mystinus) urinary bladders
Rockfish support one of the largest fisheries in California. Due to overharvesting, the California Department of Fish and Wildlife began closing the fishery from January to February in 2002 to protect females giving birth. Many male species of rockfish including blue rockfish (Sebastes mystinus) display courtship behavior prior to copulation. It has been hypothesized that pheromones may be released in the urine during courtship, thus playing a role in mate selection. In another scorpaeniform, pheromone release from the urinary bladder is associated with arterial vascularization. We hypothesized that male blue rockfish urinary bladders would be larger and have more vascularization than females. Male blue rockfish (21.23 ± 0.89 cm SL; mean ± SEM; n = 6) had urinary bladders that were 1.87 ± 0.53 cm in length, whereas females (24.33 ± 1.41 cm SL; n = 6) had urinary bladders that were 1.87 ± 0.53 cm in length. Male urinary bladder somatic index (urinary bladder weight/body weight; UBI) was significantly (p = 0.004) greater than female UBI (male 0.162 ± 0.019%, female of 0.022 ± 0.005%). Additionally, erythrocyte clusters (i.e., blood cells within arteries) were counted within the urinary bladder lumen. Males had significantly (p < 0.0001) greater vascularization within the urinary bladder (males 109.33 ± 4.72 clusters in cross section of the bladder, females 25.17 ± 1.66 clusters). This study increases our understanding of rockfish reproduction and provides a novel approach in investigating pheromone release in teleost fish.
Geological Society of America Annual Meeting, Indianapolis, IN
The implementation and use of next generation science standards-based tactile models in the K-12 educational system
In recent years, there has been a lack of Earth and Space Science (ESS) education in the K-12 system, furthermore the vast majority science education classes have centered on passive learning through lecture and textbook assignments. Scientific lab classes are often taught with well laid out science experiments that give little room for deviation from the expected outcome. This ultimately leads to a deficient understanding of how science is conducted in the real world and a high failure rate of STEM fields at the college and university level. The Next Generation Science Standards (NGSS) intends to correct the shortfall of science education by encouraging active participation and collaboration in the classroom. Within these new standards, ESS is given the same amount of content as the typical core sciences of Chemistry, Biology, and Physics. The development and usage of models to represent Earth’s processes are another benefit of the NGSS which helps students become an active participant in the classroom. This project focuses on the construction of three Earth science models for use in the K-12 classroom: an ocean garbage patch model, a glacier model, and a sinkhole model. Models are an important way for students to connect to processes that are too large, too slow, or too far away for students to observe on their own. Therefore this project also includes the design of NGSS-aligned lesson plans to accompany these models that aim to engage students in the scientific method; observation, testing, and proving a hypothesis.
American Geophysical Union, Washington D.C.
Using physical and chemical sediment characteristics to distinguish fluvial and oceanic event deposits within mid-shelf depocenters
Continental shelf stratigraphy can preserve a high-resolution record of episodic events driven by terrestrial, oceanographic and/or climate processes. Along river dominated margins, episodic events often result from fluvial floods, which produce distinct deposits on the shelf. However, for the small mountainous river systems along the US Pacific coast, storms also drive energetic ocean conditions that can increase sediment remobilization from waves and currents. Presumably, deposits from fluvial floods and wave-supported remobilization events would impact seabed processes differently, and these differences may inform our understanding of the role event deposits play in biogeochemical processes and stratigraphy. In this study we demonstrate a means by which these different types of episodic event deposits may be distinguished based on physical and chemical sediment characteristics. We collected and analyzed cores from the Monterey Bay shelf along the central California coast, focusing on areas proximal to the Salinas and Pajaro Rivers. Sediment analyses included bulk density, sedimentary fabric (CT imagery), grain size, X-ray diffraction (XRD), and X-ray fluorescence (XRF). Age control was provided through 210Pb/137Cs and 14C geochronology. We identified two-types of event deposits: Type 1, identified in upper sections of both cores, is characterized by uniform 210Pb activity with depth, increases in coarse silt and fine sand, yet lacks discernable sedimentary fabric such as bedding or laminations. Type 2 was defined primarily by sedimentary fabric (sharp contacts and internal laminations), alternating high and low bulk density layers, and increases in sand. Both types display a change in element concentrations from non-event deposition, however the changes in elemental composition are different between the cores reflecting a unique watershed signal. The Type 1 deposits we interpret to represent the combined effect of fluvial floods and shelf remobilization in wave-supported gravity flows that occurred from oceanic floods during the strong El Niño winters in the 1980s and 1990s. Type 2 deposits represent rapid settling out of terrestrially derived plumes from extreme fluvial floods such as those in 1861-1862. This study demonstrates the possibility of distinguishing between fluvial flood and wave remobilized event-deposits along the mid shelf. This distinction may provide insight into event frequency, as well as a basis to understand how these different types of episodic events may impact biogeochemical cycles.
Society for Integrative and Comparative Biology, Tampa, FL
Stayin’ alive? Assessing the ability of an intertidal seaweed to recover from repeated exposure to desiccation and high temperatures during low tide
Silvetia compressa, a canopy-forming alga, plays a vital role in rocky intertidal ecosystems as a primary producer and habitat for animals. Intertidal organisms are under seawater at high tide and exposed to terrestrial conditions at low tide. Stressors such as wind and heat during low tide can negatively affect algal physiology and subsequently biomass and canopy cover. We manipulated hydration level (values down to 17% wet mass) and body temperature (low mean = 22.79°C, high mean = 30.49°C) over two simulated low light low tides, and monitored the effect on biomass and maximum quantum yield (MQY: a measure of photosynthetic potential) over three days of recovery in simulated high tide conditions. At the end of the second low tide, hydration status was positively correlated with MQY in both low (r = 0.92) and high (r = 0.94) temperature treatments. Following 84 hours of recovery, biomass loss was minimal and not strongly associated with low tide temperature or desiccation and negative effects of desiccation on MQY disappeared, but on average, MQY in high temperature treatments was only 91.6% of that in low temperature treatments. Temporary MQY decreases following low tide desiccation indicate a reduced ability to produce sugar which could affect growth. Repeated exposure to warm low tides could slowly lower an individual’s maximum attainable photosynthetic potential. The combination of dry and warm days could ultimately lead to a decrease in canopy cover, exposing understory organisms to harsh low tide conditions with long term effects on community structure and function.
Filtration along a reticulated mesh, anatomy predicts feeding ecology in neonatal whale sharks, Rhincodon typus
The largest fish in the ocean, Rhincodon typus (Whale Shark), is one of three filter-feeding sharks. While a few studies have predicted the filtration mechanism used by R. typus, none of these studies have successfully verified this mechanism in either a live or model animal. In addition, no studies have predicted the prey selectivity in a neonatal whale shark. The objective of this study was to explore how the morphology of the filter pad separates food particles from the water. We documented the filter anatomy in neonatal whale shark specimens and calculated the freestream and transverse flow through the buccal cavity and filter pores respectively. We then created anatomically correct, scaled 3D physical models of the filter pad reticulated mesh and inserted the printed filters into a physical model of a whale shark buccal cavity. We ran a series of filtration experiments using microspheres (60 μm - 340 μm) that represent the full size range of potential zooplankton prey. Modeling the neonatal specimen allows us the rare opportunity to study feeding mechanisms in an animal that is CITES protected and rare in aquaria. Understanding the mechanism of filtration and prey selectivity in neonatal whale sharks helps to predict their ecology and likely habitat usage in the wild.
National Conference on Undergraduate Research, Kennesaw, GA
Say cheese: utilization of trail cameras brings new monitoring techniques to endangered shorebird recovery on Ormond Beach
The Pacific coast population of the western snowy plover (WSP) (Charadrius nivosus nivosus) is a small shorebird that nests and winters on the west coast beaches of North America. Although the species has evolved to survive in a dynamic beach environment, it was listed as federally threatened in 1993 because of low population numbers due to loss of habitat, human disturbance, and predation. The United States Fish and Wildlife Service (USFWS) recovery plan requires nesting outcome to be tracked to monitor progress towards species recovery goals. Standard methods rely on human-orientated monitoring instead of utilizing available technology to remotely track nesting outcome.
Trail cameras were used concurrently with traditional techniques for the 2018 nesting season on Ormond Beach in Oxnard, California. Nearly 4,000 hours were logged with over 100 predator sightings. Twelve out of 35 nests had cameras for the entire brood cycle (28 days) and one had a camera for part of the time. Out of these nests, cameras captured a definitive outcome for 67% of them (8 nests) including exact time of hatch (4 nests). Depredation of chicks was documented for 2 nests after hatching. Monitors directly witnessed only 32% of outcomes (7 nests). Two were observed actively hatching, four were seen with chicks in or near the nest, and one was spotted depredated. The remaining nest outcomes were established using deduction (68%).
Eastern Pacific Ocean Conference, Mt. Hood, OR
Distribution of microplastics at the surface and within the water column in Humboldt Bay, northern California
Plastic is a commonly used, man-made material that is highly durable, easy to produce, and used widely throughout society. The persistence of plastics results in their introduction to the oceans via river runoff from urban and industrial areas, intentional dumping, and fishing practices. This study investigates microplastics (MPs) in the size range of 0.335 to 5 mm. MPs directly affect marine ecosystems, as they are mistaken for food by marine organisms and are then transferred to humans when we consume seafood. MP concentration in the water column can vary due to river input, tidal flux, and source proximity. We hypothesized that the highest concentration of MPs within Humboldt Bay (HB) in northern California would be found in the harbor entrance (Entrance Bay), which is adjacent to a sewage treatment plant and near a solid waste transfer station. We surveyed MP concentrations within the water column and surface layer in the three sub-basins of HB. Surface and water column samples were obtained using 0.335-mm mesh neuston and ring nets, respectively. Organic material in the samples was removed via oxidation with 30% hydrogen peroxide. Density separation techniques were then used to separate plastics for microscope analysis. Preliminary results do not support our hypothesis, as air-sea interface MP concentrations are highest in North Bay (6.25x10-5 ± 4.03x10-5 plastic particles per liter (ppL)), followed by South Bay (3.48x10-5 ± 1.04x10-5 ppL), and lowest within Entrance Bay (2.23x10-5 ± 0.87x10-5 ppL). Within the water column, the highest average concentration of MPs was found in South Bay (5.81x10-5 ± 11.89x10-5 ppL), with lower concentrations in Entrance Bay (1.46x10-5 ± 0.84x10-5 ppL) and North Bay (1.21x10-5 ± 0.87x10-5 ppL). This study can help the public understand the quantity of plastic contained within HB, where it is most concentrated, and possible mitigation practices.
Association for the Sciences of Limnology and Oceanography Aquatic Science Meeting, San Juan, Puerto Rico
Characterization of ocean conditions in Monterey Bay, CA to support fisheries ecosystem research
Prevailing ocean conditions were characterized as part of NOAAs National Marine Fisheries Service 2018 Rockfish Recruitment and Ecosystem Assessment survey conducted along the California coast. Seventeen stations within Monterey Bay and the adjacent coast were sampled 7-9 June. It was expected that nekton abundance would be related to the underlying ocean conditions and chlorophyll-a (chl) concentrations. At each station, a sampling rosette equipped with a conductivity, temperature and depth (CTD) package was deployed to a maximum depth of 500 meters. Discrete water samples were collected for analysis of in vitro chl. At three locations, epipelagic micronekton were sampled by midwater trawl. Patterns of relatively cold water (11C) and elevated salinity (>33.8), indicative of upwelling, were observed in northern Monterey Bay. A north–south gradient of increasing chl from <5mg/m3 to >10 mg/m3 was observed. Greater than 80% of chl was found in cells >5-um diameter in the northern bay while in the south, only half were found in in cells >5-um. North-south declining abundance trends of the squid Doryteuthis opalescens and euphausid Thysanoessa spinifera were observed across the three trawl stations. High abundances of two jellyfish species, Chrysaora fuscescens and Aurelia spp. were encountered within Monterey Bay and interfered with trawl operations. At the three trawl stations that were sampled the highest abundances of jellyfish were found in the north. These results suggest that nekton and jellyfish abundances were not positively associated with elevated chl.
Benthic Ecology Meeting, St. Johns, Newfoundland, Canada
Evaluating the Labrisomus xanti populations on Santa Catalina Island by determining age, size ranges, densities, and habitat preference
In 2015 a strong El Niño Southern Oscillation event began affecting the NE Pacific Ocean. With increasing water temperatures, new marine species were able to expand north of native ranges and settle in new habitats. Santa Catalina Island, specifically, became home to many new species of fishes. The first sighting of the species Labrisomus xanti, or largemouth blenny, on Catalina was October 2015 and since that time these blennies have been sighted around the island. To investigate whether this species has established on Catalina, largemouth blennies were counted, sized and their sex was reported at three sites along the island. At each site, transects were placed at depths ranging from 1.5 to 6meters. Substrate type (sand, gravel, cobble, boulders 10-100cm, bench) was recorded along each transect. Observations showed that there are multiple size ranges among sites, depths and sexes of largemouth blennies. Individuals were then collected and aged based on otolith extractions. We found a significant difference in densities among sites and habitat preference was significant based on substrate. These densities, ages and habitat preferences are important observations because if largemouth blennies are established and settling permanently on Catalina they may begin competing with native species for territory and resources.
Heat sock proteins in Tigriopus californicus
Do Tegula react to different predators based on their history of exposure to those predators
Moray eel neuroanatomy and spatial cognition: cross species examination of Rhinomuraena quaesita and Anguilla anguilla
Something in the water: environmental DNA profiling of tide pool biodiversity
Testing for microplastics and glyphosate contamination levels throughout the conventional and organic brewing processes
Is the predator-avoidance response of Nucella lamellosa impaired while in low pH conditions
The effects of ocean acidification on the developing larval stages of the crab, Petrolisthes cinctipes
Wildlife monitoring in California State University Channel Islands Regional Park: a restoration study post-wildfire destruction and succession
Creating a maraponics system to effectively grow Salicornia pacifica and remove nitrogenous wastes
Presence of Portunion conformis in Humboldt Bay
Acclimation response of Mytilus californianus to increased air temperature
Establishment of symbiosis in the model sea anemone Exaiptasia pallida: analyzing host specificity of dinoflagellates under heat stress
Use of induced spawning to determine sex chromosome in red lionfish (Pterois volitans)
3-Dimensional reconstruction of surfperch reproductive anatomy using a medical diagnostic tool
Testing the mechanisms of bubble nets
Investigating the impact of zoo-inquiry projects for marine exhibits in introductory chemistry laboratories
The influence of conductivity on methane and carbon dioxide fluxes in a California tidal wetland
Acute toxicity of ammonia to Alitta brandti
Estimating growth and mortality rates of Megastraea undosa in Southern California
Tagging and identifying white sharks at Guadalupe Island
Distribution of surficial slip along the Santa Cruz Island fault based on LIDAR measurements
The effect of ocean acidification on the growth and development of Artemia franciscana
Testing for microplastics and glyphosate contamination levels throughout the conventional and organic brewing processes
Size estimates of white sharks (Carcharodon carcharias) in Guadalupe Island, Mexico
Asexual reproduction of sea anemone Exaiptasia pallida under varying light conditions
Polyaromatic hydrocarbons and their oxygenated metabolites target ion channels
Invertebrate surveys of Morro Bay
Size matters: comparative morphology of rockfish urogenital papilla
Mapping erosion along Rancho Pales Verde coast using geospatial technology
A cross-species comparison of the lateral pallium in Gymothorax saxicola and Gymnothorax undulatus to determine spatial cognitive development
The impacts of dredging on Moray Bay biodiversity
Western pond turtle captive breeding genetics
Phycological Society of America and International Society of Protistologists, Vancouver, BC, Canada
Spatial patterns of genetic structure in Mastocarpus stellatus (Rhodophyta)
Mastocarpus stellatus occurs in dense patches on many rocky shores on both eastern and western coastlines of the North Atlantic Ocean. The life cycle of M. stellatus consists of sexual generations alternating between upright, haploid gametophytes and diploid crustose tetrasporophytes, and in many northerly populations, a diploid asexual life cycle in which female fronds give rise directly to diploid females. Our research examines the spatial genetic structure of mapped individuals of M. stellatus within and among shores from seven sites in France and four sites in Maine using 15 DNA microsatellite markers. DNA was extracted from vegetative tissue of crusts and the stipes of fronds. Signatures of diploid genotypes (i.e., heterozygous at one or more microsatellite loci) indicated that almost all fronds collected in Maine were asexual at most sites. Reduced genetic diversity and high frequency of diploid frond genotypes relative to Eastern Atlantic populations suggest that clonality is the primary mode of reproduction for M. stellatus lineages in the Northwest Atlantic. In France, high levels of genetic structure were observed between sexual (single allele at all loci) and asexual lineages within populations. There was no evidence of isolation by distance among pairwise combinations of individuals within sites (0.05-50 m distances). Our results suggest that short distance dispersal does not hinder gene flow within populations of M. stellatus, but reproductive isolation between sexual and asexual lineages drives their divergence.