Browsing by Author "Ghalambor, Cameron, advisor"

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Embargo
Changes in functional structure of aquatic insect communities across environmental gradients in mountain streams
(Colorado State University. Libraries, 2024) Gutierrez, Carolina, author; Poff, N. LeRoy, advisor; Ghalambor, Cameron, advisor; Neuwald, Jennifer, committee member; Webb, Colleen, committee member
This study investigates the functional diversity of aquatic insect communities across environmental gradients within Rocky Mountain headwater streams, aiming to better understand how elevation, water temperature, and canopy cover shape the structure and dynamics of these communities. Functional diversity (FD) is defined here as the range, distribution, and relative abundance of organismal traits, which together provide deeper insight into ecosystem functionality than species diversity alone. FD was quantified through three primary metrics: functional richness (FRic), functional evenness (FEve), and functional divergence (FDiv), each capturing distinct aspects of how species contribute to ecosystem functioning. This multidimensional approach enables a nuanced examination of how aquatic insect communities respond to various environmental stressors and spatial constraints, particularly as altitudinal changes present unique challenges in terms of temperature variability and resource availability. Field data were collected from twenty-four stream sites distributed across elevation bands ranging from 1,500 to 3,500 meters. Sites were replicated in three different drainage systems to account for regional variation, with insect specimens collected and assessed for twenty functional traits. These traits included parameters such as voltinism (number of life cycles per year), adult lifespan, emergence synchronization, and dispersal ability, all of which are critical in determining an insect's role in the ecosystem. Canopy cover and water temperature were also measured to evaluate how localized microclimates and light availability influenced community composition. Results revealed a significant decline in functional richness with increasing elevation, with the steepest reductions observed in streams with sparse canopy cover. Functional richness was highest in areas where canopy cover ranged between 65-78%, and water temperature was between 8°C and 15°C, suggesting that moderate canopy cover and specific thermal conditions support more functionally diverse communities. Functional evenness and divergence, while showing less pronounced patterns, indicated that the most extreme trait values are critical for resilience in these systems, particularly under fluctuating environmental conditions. Trophic interactions further illustrate the importance of specific functional groups, such as predators, grazers, and filterers, in shaping community structure. The analysis of beta diversity demonstrated substantial turnover in functional traits across elevation gradients, emphasizing the heterogeneity of insect communities within low-order, high-altitude streams and reinforcing the role of environmental filtering in community assembly. These findings highlight the vulnerability of headwater stream ecosystems to environmental changes and underscore the importance of functional diversity metrics in ecological monitoring and conservation efforts. Overall, this study contributes to our understanding of how functional environmental gradients structure diversity and provides a foundation for comparative studies on functional diversity in tropical versus temperate mountain stream ecosystems, particularly in the context of global biodiversity conservation.
Open Access
Flexible phenotypes: the diverse roles of phenotypic plasticity during adaptive evolution in experimental populations of Trinidadian guppies
(Colorado State University. Libraries, 2015) Handelsman, Corey, author; Ghalambor, Cameron, advisor; Angeloni, Lisa, committee member; Antolin, Michael, committee member; Myrick, Christopher, committee member
To view the abstract, please see the full text of the document.
Open Access
Parasites of two closely related Poeciliid species across a salinity gradient on the island of Trinidad: implications for geographic range limits
(Colorado State University. Libraries, 2018) Robison, Porsche, author; Ghalambor, Cameron, advisor; McGrew, Ashley K., committee member; Schaffer, Paula, committee member; Peers, Graham, committee member
Parasite communities can vary greatly both within and amongst host populations. Many factors may be responsible for this variation in parasite diversity, and parasite-host relationships are of great ecological importance as parasites can alter host behavior, impact population demography, and drive co-evolutionary dynamics. One long-standing ecological question is how these parasite-host interactions shape mutual geographic distributions, which are also impacted by various abiotic and biotic factors. However, few studies have investigated how parasite communities change across environmental gradients and different host species, or how parasite abundance changes within and outside the host geographic range. The island of Trinidad provides a model system that can be used to address these questions. On this island, the tropical fish Poecilia reticulata inhabits mountainous and lowland freshwater streams but avoids brackish waters. A close relative, Poecilia picta inhabits both lowland freshwater and brackish water streams. To date, no study has investigated how internal parasite communities vary across this salinity gradient or between these two closely related host species with overlapping geographic ranges. In lab studies, P. reticulata has been shown to be physiologically tolerant of brackish water, suggesting some other environmental factor may limit their dispersal and range expansion into brackish waters. Here we investigated how internal parasite diversity changes between 1) natural P. reticulata and P. picta populations in freshwater, 2) natural populations of P. picta in fresh and brackish water sites, and3) P. reticulata, experimentally exposed to fresh and brackish water conditions. We found the prevalence of digenean trematode metacercariae to be 100% across three different river systems for both host species, however, mean metacercarial abundance differed significantly by river. Based on morphological differences in the metacercariae, we identified three distinct morphospecies. All three morphospecies were found in freshwater P. reticulata and P. picta. However, mean abundance of parasites varied across the two host species with P. reticulata harboring more parasites, on average, compared to P. picta. All three morphospecies were also found in P. picta in brackish water, but the total mean metacercarial abundance of P. picta was found to be increased in brackish compared to freshwater sites. Collectively, these results suggest that the three morphospecies utilize both hosts and they are limited in their geographic distribution by salinity. Still, the internal abundance of parasites varies between the two hosts depending on the salinity. We tested whether these same parasites may be limiting the distribution of P. reticulata to freshwater, by experimentally exposing P. reticulata populations to field-collected brackish water. We assumed field-collected brackish water contains live cercaria and conducted exposures for a period of seven days. Compared to controls exposed to field-collected freshwater, there was a significant increase in the internal metacercarial abundance, along with an increase in mortality amongst the brackish water exposed group. These results suggest that movement of P. reticulata into novel brackish environments may be inhibited by increased parasitism; however, further investigations are warranted to better understand the mechanisms that determine the geographic distributions of parasites and their hosts.