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Phylogeography of the Coastal Mosquito Aedes togoi across Climatic Zones: Testing an Anthropogenic Dispersal Hypothesis

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

The coastal mosquito Aedes togoi occurs more or less continuously from subarctic to subtropic zones along the coasts of the Japanese islands and the East Asian mainland. It occurs also in tropical Southeast Asia and the North American Pacific coast, and the populations there are thought to have been introduced from Japan by ship. To test this hypothesis, the genetic divergence among geographic populations of A. togoi was studied using one mitochondrial and three nuclear gene sequences. We detected 71 mitochondrial haplotypes forming four lineages, with high nucleotide diversity around temperate Japan and declining towards peripheral ranges. The major lineage (L1) comprised 57 haplotypes from temperate and subarctic zones in Japan and Southeast Asia including southern China and Taiwan. Two other lineages were found from subtropical islands (L3) and a subarctic area (L4) of Japan. The Canadian population showed one unique haplotype (L2) diverged from the other lineages. In the combined nuclear gene tree, individuals with mitochondrial L4 haplotypes diverged from those with the other mitochondrial haplotypes L1—L3; although individuals with L1—L3 haplotypes showed shallow divergences in the nuclear gene sequences, individuals from Southeast Asia and Canada each formed a monophyletic group. Overall, the genetic composition of the Southeast Asian populations was closely related to that of temperate Japanese populations, suggesting recent gene flow between these regions. The Canadian population might have originated from anthropogenic introduction from somewhere in Asia, but the possibility that it could have spread across the Beringian land bridge cannot be ruled out.

Document type: 
Article
File(s): 

Juvenile Salmon Usage of the Skeena River Estuary

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Migratory salmon transit estuary habitats on their way out to the ocean but this phase of their life cycle is more poorly understood than other phases. The estuaries of large river systems in particular may support many populations and several species of salmon that originate from throughout the upstream river. The Skeena River of British Columbia, Canada, is a large river system with high salmon population- and species-level diversity. The estuary of the Skeena River is under pressure from industrial development, with two gas liquefaction terminals and a potash loading facility in various stages of environmental review processes, providing motivation for understanding the usage of the estuary by juvenile salmon. We conducted a juvenile salmonid sampling program throughout the Skeena River estuary in 2007 and 2013 to investigate the spatial and temporal distribution of different species and populations of salmon. We captured six species of juvenile anadromous salmonids throughout the estuary in both years, and found that areas proposed for development support some of the highest abundances of some species of salmon. Specifically, the highest abundances of sockeye (both years), Chinook in 2007, and coho salmon in 2013 were captured in areas proposed for development. For example, juvenile sockeye salmon were 2–8 times more abundant in the proposed development areas. Genetic stock assignment demonstrated that the Chinook salmon and most of the sockeye salmon that were captured originated from throughout the Skeena watershed, while some sockeye salmon came from the Nass, Stikine, Southeast Alaska, and coastal systems on the northern and central coasts of British Columbia. These fish support extensive commercial, recreational, and First Nations fisheries throughout the Skeena River and beyond. Our results demonstrate that estuary habitats integrate species and population diversity of salmon, and that if proposed development negatively affects the salmon populations that use the estuary, then numerous fisheries would also be negatively affected.

Document type: 
Article
File(s): 

Location Is Everything: Evaluating the Effects of Terrestrial and Marine Resource Subsidies on an Estuarine Bivalve

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Estuaries are amongst the world’s most productive ecosystems, lying at the intersection between terrestrial and marine environments. They receive substantial inputs from adjacent landscapes but the importance of resource subsidies is not well understood. Here, we test hypotheses for the effects of both terrestrial- and salmon-derived resource subsidies on the diet (inferred from stable isotopes of muscle tissue), size and percent nitrogen of the soft-shell clam (Mya arenaria), a sedentary estuarine consumer. We examine how these relationships shift across natural gradients among 14 estuaries that vary in upstream watershed size and salmon density on the central coast of British Columbia, Canada. We also test how assimilation and response to subsidies vary at smaller spatial scales within estuaries. The depletion and enrichment of stable isotope ratios in soft-shell clam muscle tissue correlated with increasing upstream watershed size and salmon density, respectively. The effects of terrestrial- and salmon-derived subsidies were also strongest at locations near stream outlets. When we controlled for age of individual clams, there were larger individuals with higher percent nitrogen content in estuaries below larger watersheds, though this effect was limited to the depositional zones below river mouths. Pink salmon exhibited a stronger effect on isotope ratios of clams than chum salmon, which could reflect increased habitat overlap as spawning pink salmon concentrate in lower stream reaches, closer to intertidal clam beds. However, there were smaller clams in estuaries that had higher upstream pink salmon densities, possibly due to differences in habitat requirements. Our study highlights the importance of upstream resource subsidies to this bivalve species, but that individual responses to subsidies can vary at smaller scales within estuaries.

Document type: 
Article
File(s): 

Do American Dippers Obtain a Survival Benefit from Altitudinal Migration?

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Studies of partial migrants provide an opportunity to assess the cost and benefits of migration. Previous work has demonstrated that sedentary American dippers (residents) have higher annual productivity than altitudinal migrants that move to higher elevations to breed. Here we use a ten-year (30 period) mark-recapture dataset to evaluate whether migrants offset their lower productivity with higher survival during the migration-breeding period when they occupy different habitat, or early and late-winter periods when they coexist with residents. Mark-recapture models provide no evidence that apparent monthly survival of migrants is higher than that of residents at any time of the year. The best-supported model suggests that monthly survival is higher in the migration-breeding period than winter periods. Another well-supported model suggested that residency conferred a survival benefit, and annual apparent survival (calculated from model weighted monthly apparent survival estimates using the Delta method) of residents (0.511 ± 0.038SE) was slightly higher than that of migrants (0.487 ± 0.032). Winter survival of American dippers was influenced by environmental conditions; monthly apparent survival increased as maximum daily flow rates increased and declined as winter temperatures became colder. However, we found no evidence that environmental conditions altered differences in winter survival of residents and migrants. Since migratory American dippers have lower productivity and slightly lower survival than residents our data suggests that partial migration is likely an outcome of competition for limited nest sites at low elevations, with less competitive individuals being forced to migrate to higher elevations in order to breed.

Document type: 
Article
File(s): 

Effects of Salmon-Derived Nutrients and Habitat Characteristics on Population Densities of Stream-Resident Sculpins

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Movement of nutrients across ecosystem boundaries can have important effects on food webs and population dynamics. An example from the North Pacific Rim is the connection between productive marine ecosystems and freshwaters driven by annual spawning migrations of Pacific salmon (Oncorhynchus spp). While a growing body of research has highlighted the importance of both pulsed nutrient subsidies and disturbance by spawning salmon, their effects on population densities of vertebrate consumers have rarely been tested, especially across streams spanning a wide range of natural variation in salmon densities and habitat characteristics. We studied resident freshwater prickly (Cottus asper), and coastrange sculpins (C. aleuticus) in coastal salmon spawning streams to test whether their population densities are affected by spawning densities of pink and chum salmon (O. gorbuscha and O. keta), as well as habitat characteristics. Coastrange sculpins occurred in the highest densities in streams with high densities of spawning pink and chum salmon. They also were more dense in streams with high pH, large watersheds, less area covered by pools, and lower gradients. In contrast, prickly sculpin densities were higher in streams with more large wood and pools, and less canopy cover, but their densities were not correlated with salmon. These results for coastrange sculpins provide evidence of a numerical population response by freshwater fish to increased availability of salmon subsidies in streams. These results demonstrate complex and context-dependent relationships between spawning Pacific salmon and coastal ecosystems and can inform an ecosystem-based approach to their management and conservation.

Document type: 
Article
File(s): 

Poecilia picta, a Close Relative to the Guppy, Exhibits Red Male Coloration Polymorphism: A System for Phylogenetic Comparisons

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Studies on the evolution of female preference and male color polymorphism frequently focus on single species since traits and preferences are thought to co-evolve. The guppy, Poecilia reticulata, has long been a premier model for such studies because female preferences and orange coloration are well known to covary, especially in upstream/downstream pairs of populations. However, focused single species studies lack the explanatory power of the comparative method, which requires detailed knowledge of multiple species with known evolutionary relationships. Here we describe a red color polymorphism in Poecilia picta, a close relative to guppies. We show that this polymorphism is restricted to males and is maintained in natural populations of mainland South America. Using tests of female preference we show female P. picta are not more attracted to red males, despite preferences for red/orange in closely related species, such as P. reticulata and P. parae. Male color patterns in these closely related species are different from P. picta in that they occur in discrete patches and are frequently Y chromosome-linked. P. reticulata have an almost infinite number of male patterns, while P. parae males occur in discrete morphs. We show the red male polymorphism in P. picta extends continuously throughout the body and is not a Y-linked trait despite the theoretical prediction that sexually-selected characters should often be linked to the heterogametic sex chromosome. The presence/absence of red male coloration of P. picta described here makes this an ideal system for phylogenetic comparisons that could reveal the evolutionary forces maintaining mate choice and color polymorphisms in this speciose group.

Document type: 
Article
File(s): 

Ranking Mammal Species for Conservation and the Loss of Both Phylogenetic and Trait Diversity

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

The 'edge of existence' (EDGE) prioritisation scheme is a new approach to rank species for conservation attention that aims to identify species that are both isolated on the tree of life and at imminent risk of extinction as defined by the World Conservation Union (IUCN). The self-stated benefit of the EDGE system is that it effectively captures unusual 'unique' species, and doing so will preserve the total evolutionary history of a group into the future. Given the EDGE metric was not designed to capture total evolutionary history, we tested this claim. Our analyses show that the total evolutionary history of mammals preserved is indeed much higher if EDGE species are protected than if at-risk species are chosen randomly. More of the total tree is also protected by EDGE species than if solely threat status or solely evolutionary distinctiveness were used for prioritisation. When considering how much trait diversity is captured by IUCN and EDGE prioritisation rankings, interestingly, preserving the highest-ranked EDGE species, or indeed just the most threatened species, captures more total trait diversity compared to sets of randomly-selected at-risk species. These results suggest that, as advertised, EDGE mammal species contribute evolutionary history to the evolutionary tree of mammals non-randomly, and EDGE-style rankings among endangered species can also capture important trait diversity. If this pattern holds for other groups, the EDGE prioritisation scheme has greater potential to be an efficient method to allocate scarce conservation effort.

Document type: 
Article
File(s): 

Supplementary Material: Phylogeny of all seeded plant families

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2015-10-05
Abstract: 

Climate change is driving rapid and accelerating shifts in range limits, both poleward expansions and equatorward contractions.  However, many species are falling behind the pace of change in their dispersal into newly suitable habitats and now show “climate debts”, lags between predicted and observed range expansions under changing climates. Failure to track changing climates may be due to interspecific interactions such as particular food availability for specialists, abiotic barriers such as mountain ranges, or intrinsic traits such as dispersal limitation. A trait-based analysis of climate change performance would help identify causes of climate debt.

To understand the correlates of climate debt within a large clade of organisms we use historical and modern observations of butterflies from western Canada as a case study to construct and project individual climate-based environmental niche models. By comparing projected distributions based on historical records to observed modern distributions we are able to construct estimates of climate debt and evaluate the effect of dispersal ability, diet breadth and a proxy for range size on these species' measured climate debt.

High levels of climate debt are accumulating within the butterflies of Western Canada, independently of dispersal ability, diet breadth and phylogeny. Range size emerges as the only variable that significantly reduces climate debt, suggesting that more narrowly-ranged species may be at risk of being squeezed out by both a reduction of suitable habitat in their current range and the failure to colonize newly available habitat. These findings underscore the need to investigate potential landscape-level determinants of climate debt that may be limiting range expansions in this group.

Document type: 
Dataset

Supplemental Material - 1000 randomly-chosen candidate topologies for the Canadian butterfly phylogeny

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2015-10-05
Abstract: 

Climate change is driving rapid and accelerating shifts in range limits, both poleward expansions and equatorward contractions. However, many species are falling behind the pace of change in their dispersal into newly suitable habitats and now show “climate debts”, lags between predicted and observed range expansions under changing climates. Failure to track changing climates may be due to interspecific interactions such as particular food availability for specialists, abiotic barriers such as mountain ranges, or intrinsic traits such as dispersal limitation. A trait-based analysis of climate change performance would help identify causes of climate debt.

To understand the correlates of climate debt within a large clade of organisms we use historical and modern observations of butterflies from western Canada as a case study to construct and project individual climate-based environmental niche models. By comparing projected distributions based on historical records to observed modern distributions we are able to construct estimates of climate debt and evaluate the effect of dispersal ability, diet breadth and a proxy for range size on these species' measured climate debt.

High levels of climate debt are accumulating within the butterflies of Western Canada, independently of dispersal ability, diet breadth and phylogeny. Range size emerges as the only variable that significantly reduces climate debt, suggesting that more narrowly-ranged species may be at risk of being squeezed out by both a reduction of suitable habitat in their current range and the failure to colonize newly available habitat. These findings underscore the need to investigate potential landscape-level determinants of climate debt that may be limiting range expansions in this group.

Document type: 
Dataset
Other

Valuing Species on the Cheap

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Document type: 
Article
Dataset