Population Ecology II and Systematics
Presiding: A G Hildrew, Queen Mary, University of London; C Smith, Brigham Young University
NB52C-01 10:30h
Landscape, Population Structure and Genetic Relatedness in two Contrasting Caddisflies
We used microsatellite markers to examine the genetic relatedness of populations of two polycentropodid caddisflies over substantial areas of Great Britain. One (the small-bodied Polycentropus flavomaculatus) is found in large, continuous populations in larger streams and rivers, while the other (the large-bodied Plectrocnemia conspersa) is found in small, fragmented larval habitats in the extreme headwaters. In P. flavomaculatus, populations were genetically distinct between almost all pairs of sites, suggesting limited dispersal by adults between rivers. In P. conspersa, on the other hand, populations were homogenous in lowland England over distances approaching 100km, inferring widespread adult dispersal. In upland north-western England, however, P conspersa populations were more distinct in a landscape where streams are separated by land of higher altitude. This infers that high relief may act as a barrier to adult dispersal. Other evidence suggests that there may be other barriers to adult dispersal through the landscape, beyond the effect of high ground alone, that could disrupt dispersal by the adults of species living in patchily distributed larval habitats
NB52C-02 10:45h
Phylogenetic Relationships of Cottus beldingi in the Basin and Range and Colorado Plateau of Western North America
Cottus beldingi (Paiute sculpin) is found in scattered populations across the Western United States. Their distribution should be related to ancient river connections. To investigate these relationships, C. beldingi were collected from 14 locations in Nevada, Utah, Idaho, Colorado, and Wyoming. Three regions of mitochondrial DNA were sequenced including a 363 bp segment of ND4-L/ND4 gene, the cyt b gene, and the d-loop. Phylogenies were constructed using Maximum Parsimony (PAUP), Maximum Likelihood (PAML), and Bayesian analysis (MrBayes). Preliminary analyses of the ND4 gene show Lahonta Basin (Nevada) C. beldingi have the most basal relationship in phylogenies based on Maximum Parsimony and Maximum Likelihood. C. beldingi in the Lost River system of Idaho, Eagle River of Colorado, and the Provo and Weber Rivers of the Bonneville Basin form a clade. Populations from the Upper Snake River of Idaho and Wyoming, and the Logan River drainage form a separate clade. The latter clade may reflect the capture of the Bear River and subsequent Bonneville flood 18,000 to 30,000 years ago. The former clade is likely a result of older drainage connections.
NB52C-03 11:00h
Distribution and Feeding Preferences of Newfoundland larval Hydropsychidae
Caddisflies of the family Hydropsychidae (Trichoptera) are widely distributed across North America (145 species), however the large scale distribution of the impoverished Newfoundland fauna (8 species) is unknown. Low species diversity and irregular stream profiles on the island provide a template for community distribution. Sampling a variety of rivers at lake outlets and downstream in forested and barren habitats revealed the influence of landscape on Hydropsychidae distribution and abundance. Forested and barren streams supported the same species of hydropsychids but barren streams generally had much lower densities. Community composition changed on a longitudinal gradient. Extensive measurements of nutrient quantity (phytoplankton, zooplankton, periphyton) did not strongly correlate with community composition or landscape effects. The literature suggests that nutrient quality may have a stronger influence due to premised resource partitioning. One method of investigation is lipid analysis, where nutrient composition is determined via free fatty acid biomarkers. Preliminary results indicate that the fauna are general opportunists, feeding over a range of trophic levels, with outlet community feeding habits being distinctive from downstream. Current trophic categorizations of hydropsychids are questioned.
NB52C-04 11:15h
How to Compare Biomass and Drift of the River Benthos?
Drift flux per unit bottom area (Db) of different river reaches can be expediently estimated as biomass of transported organisms at a particular collection time through the cross sectional area of water flow for width of 1 m and height equals to the depth of river part (H, m) at the time of sampling (Db, mg/m2/day). In this case, independent of river depth, water velocity and discharge Db for 24 h will be defined as simple multiplication of two parameters: Db = L(m) × Mb (mg/m3/day), where L is distance of drift and Mb is daily migratory activity of the aquatic organisms equals biomass of organisms lifted during 24 h from 1 m2 of the river bottom into the water column with volume 1 m2 × H. This method allows one to calculate specific drift rate (Dcb), which takes into account benthic density on the river bottom and is estimated with units of inverse time, i.e., the fraction of benthic biomass that enters the drift in 24 hours. So Db = Db/B, where B is biomass of benthos, mg/1 m2 The specific drift rate calculated for various groups of invertebrates surprisingly showed a negative correlation between Dcb and benthic biomass. Thus, our results contradict the generally accepted hypothesis describing drift as competition among aquatic organisms for food and substratum.
NB52C-05 11:30h
Taxonomic Resolution as a Conceptual Problem for Understanding Ecological Science.
The results of ecological analyses can vary with the taxonomic resolution(s) used to sort and quantify the organisms studied. It seems intuitive that the finest unit of taxonomy results in the finest discrimination of ecological processes, and this is certainly true in many cases (e.g. Hawkins 2000, Attayde 2001). However, other important work suggests that some ecological processes (e.g. Bowman 1997) or concepts (e.g. Schoener 1986, Olsgard 1998) are only supported by analysis at supra-specific taxonomic resolution. In fact, taxonomic levels above species are often necessary for detecting certain ecological relationships, such as key measurements of food webs (Vanderklift 1998) or stability of ecological communities over time (Bowman 1997). If some levels of organization result in different ecological outcomes, two questions are immediately raised. First, why do these levels lead to different outcomes, and second, what is the basis of choosing one resolution over another? I will address the first question by outlining four aspects of the problematic relationship between taxonomy and ecology: taxonomic variance, taxonomic heterogeneity, and taxonomic ambiguity both within and between groups. I aim to show that these interactions suggest a dependence relationship of ecological outcomes on taxonomic concepts.
NB52C-06 11:45h
Molecular phylogeny of the Drusinae (Trichoptera: Limnephilidae): preliminary results
We examine the phylogenetic relationships within the subfamily of the Drusinae using molecular markers. Sequence data from two mitochondrial loci (mitochondrial cytochrome oxidase I, mitochondrial ribosomal large subunit) are used to infer the relationships within and among the genera of the Drusinae. Sequence data were generated for 21 taxa from five genera from the subfamily. The molecular data were analyzed using a Bayesian Markov Chain Monte Carlo and a Maximum Parsimony approach for both single gene and combined data sets. Several hypotheses of relationships previously inferred based on morphological characters were tested. The study revealed a very close relationship between Drusus discolor and D. romanicus suggesting that divergence between these two species occurred recently. The relationships inferred by molecular data suggest that larval morphology may be an important taxonomic character, which has often been neglected. The data also indicate that the genera Ecclisopteryx and Drusus are polyphyletic with respect to one another.