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126 results for “Ecological selection”

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Data from: Selection on a genetic polymorphism counteracts ecological speciation in a stick insect

The interplay between selection and aspects of the genetic architecture of traits (such as linkage, dominance, and epistasis) can either drive or constrain speciation. Despite accumulating evidence that speciation can progress to "intermediate" stages—with populations evolving only partial reproductive isolation—studies describing selective mechanisms that impose constraints on speciation are more rare than those describing drivers. The stick insect Timema cristinae provides an example of a system in which partial reproductive isolation has evolved between populations adapted to different host plant environments, in part due to divergent selection acting on a pattern polymorphism. Here, we demonstrate how selection on a green/melanistic color polymorphism counteracts speciation in this system. Specifically, divergent selection between hosts does not occur on color phenotypes because melanistic T. cristinae are cryptic on the stems of both host species, are resistant to a fungal pathogen, and have a mating advantage. Using genetic crosses and genome-wide association mapping, we quantify the genetic architecture of both the pattern and color polymorphism, illustrating their simple genetic control. We use these empirical results to develop an individual-based model that shows how the melanistic phenotype acts as a "genetic bridge" that increases gene flow between populations living on different hosts. Our results demonstrate how variation in the nature of selection acting on traits, and aspects of trait genetic architecture, can impose constraints on both local adaptation and speciation.

opencc-zeroDec 2014View details →

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Data from: Machine learning identifies ecological selectivity patterns across the end-Permian mass extinction

The end-Permian mass extinction occurred alongside a large swathe of environmental changes that are often invoked as extinction mechanisms, even when a direct link is lacking. One way to elucidate the cause(s) of a mass extinction is to investigate extinction selectivity as it can reveal critical information on organismic traits as key determinants of extinction and survival. Here we show that machine learning algorithms, specifically gradient boosted decision trees, can be used to identify determinants of extinction as well as predict extinction risk. To understand which factors led to the end-Permian mass extinction during an extreme global warming event, we quantified the ecological selectivity of marine extinctions in the well-studied South China region. We find that extinction selectivity varies between different groups of organisms and that a synergy of multiple environmental stressors best explains the overall end-Permian extinction selectivity pattern. Extinction risk was greater for genera that had a low species richness, had narrow bathymetric ranges limited to deep-water habitats, had a stationary mode of life, possessed a siliceous skeleton or, less critically, had calcitic skeletons. These selective losses directly link the extinction to the environmental effects of rapid injections of carbon dioxide into the ocean-atmosphere system, specifically the combined effects of expanded oxygen minimum zones, rapid warming, and potentially ocean acidification.

opencc-zeroDec 2021View details →

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An innovative approach combining metabarcoding and ecological interaction networks for selecting candidate biological control agents

Classical biological control (CBC) can be used to decrease the density of invasive species to below an acceptable ecological and economic threshold. Natural enemies specific to the invasive species are selected from its native range and released into the invaded range. This approach has drawbacks, despite the performance of specificity tests to ensure its safety, because the fundamental host range defined under controlled conditions does not represent the actual host range in natura, and these tests omit indirect interactions within community. We focus on Sonchus oleraceus (Asteraceae), a weed species originating from Western Palearctic that is invasive in many countries and notably in Australia. We explore how analyses of interaction network within its native range can be used to 1) inventory herbivores associated to the target plant, 2) characterize their ecological host ranges, and 3) guide the selection of candidate biocontrol agents considering interactions with species from higher trophic levels. Arthropods were collected from plant community sympatric to S. oleraceus, in three bioclimatic regions, and interactions were inferred by a combination of molecular and morphological approaches. The networks reconstructed were structured in several trophic levels from basal species (plant community), to intermediate and top species (herbivorous arthropods and their natural enemies). The subnetwork centered on S. oleraceus related interactions contained 116 taxa and 213 interactions. We identified 47 herbivores feeding on S. oleraceus, 15 of which were specific to the target species. Some discrepancies with respect to published findings or conventional specificity tests suggested possible insufficient sampling effort for the recording of interactions or the existence of cryptic species. Among potential candidate agents, 6 exhibited interactions with natural enemies. Synthesis and applications: Adopting a network approach as prerequisite step of the classical biological control program can provide a rapid screening of potential agents to be tested in priority. Once ecological host range defined, we suggest that priority should be given to agent used by a minimum species, and, when they exist, to agents that possess enemies from the most distant taxonomical group from those occurring in the range of introduction.

opencc-zeroMar 2022View details →

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Data for: The visual ecology of selective predation: Are unhealthy hosts less stealthy hosts?

Predators can strongly influence disease transmission and evolution, particularly when they prey selectively on infected hosts. Although selective predation has been observed in numerous systems, why predators select infected prey remains poorly understood. Here, we use a mathematical model of predator vision to test a longstanding hypothesis about the mechanistic basis of selective predation in a Daphnia-microparasite system, which serves as a model for the ecology and evolution of infectious diseases. Bluegill sunfish feed selectively on Daphnia infected by a variety of parasites, particularly in water uncolored by dissolved organic carbon. The leading hypothesis for selective predation in this system is that infection-induced changes in the transparency of Daphnia render them more visible to bluegill. Rigorously evaluating this hypothesis requires that we quantify the effect of infection on the visibility of prey from the predator's perspective, rather than our own. Using a model of the bluegill visual system, we show that three common parasites, Metschnikowia bicuspidata, Pasteuria ramosa and Spirobacillus cienkowskii, decrease the transparency of Daphnia, rendering infected Daphnia darker against a background of downwelling light. As a result of this increased brightness contrast, bluegill can see infected Daphnia at greater distances than uninfected Daphnia - between 19-33% further, depending on the parasite. Pasteuria and Spirobacillus also increase the chromatic contrast of Daphnia. These findings lend support to the hypothesis that selective predation by fish on infected Daphnia could result from the effects of infection on Daphnia's visibility. However, contrary to expectations, the visibility of Daphnia was not strongly impacted by water color in our model. Our work demonstrates that models of animal visual systems can be useful in understanding ecological interactions that impact disease transmission.

opencc-zeroJun 2022View details →

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Data for: Evolutionary interactions between thermal ecology and sexual selection

Thermal ecology and mate competition are both pervasive features of ecological adaptation. A surge of recent work has uncovered the diversity of ways in which temperature affects mating interactions and sexual selection. However, the potential for thermal biology and reproductive ecology to evolve together as organisms adapt to their thermal environment has been underappreciated. Here, we develop a series of hypotheses regarding (1) not only how thermal ecology affects mating system dynamics, but also how mating dynamics can generate selection on thermal traits; and (2) how the thermal consequences of mate competition favor the reciprocal co-adaptation of thermal biology and sexual traits. We discuss our hypotheses in the context of both pre-copulatory and post-copulatory processes. We also call for future work integrating experimental and phylogenetic comparative approaches to understand evolutionary feedbacks between thermal ecology and sexual selection. Overall, studying reciprocal feedbacks between thermal ecology and sexual selection may be necessary to understand how organisms have adapted to the environments of the past and could persist in the environments of the future.

opencc-zeroJul 2022View details →

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Shell colour diversification induced by ecological release: a shift in natural selection after a migration event

Ecological release is often attributed to the rapid adaptive diversification of phenotypic traits. However, it is not well understood how natural selection changes its strength and direction through the process of ecological release. Herein, we demonstrated how shell colour of the Japanese land snail Euhadra peliomphala simodae has diversified via a shift in natural selection due to ecological release after migration from the mainland to an island. This snail's shell colour diversified on the island due to disruptive selection after migration from the mainland. We used trail-camera traps to identify the cause of natural selection on both the mainland and island. We then conducted a mark-recapture experiment while collecting microhabitat use data. In total, we captured and marked around 1700 snails on the mainland, some of which were preyed upon by an unknown predator. The trail-camera traps showed that the predator is the large Japanese field mouse Apodemus speciosus, and the predatory frequency was higher on the mainland than on the island. However, this predation did not correlate with shell colour. Microhabitat use on the island was more extensive than on the mainland, with snails on the island using both ground and arboreal microhabitats. A Bayesian estimation showed that the stabilising selection on shell colour came from factors other than predation. Our results suggest that the course of natural selection was modified due to ecological release after migration from the mainland, explaining one cause of the phenotypic diversification.

opencc-zeroAug 2022View details →

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Ecology and evolution of competitive trait variation in natural phytoplankton communities under selection

Competition for limiting resources is a major force structuring ecological communities. Species minimum resource requirements (R*s) can predict competitive outcomes and evolve under selection in simple communities under controlled conditions. However, whether R*s predict competitive outcomes or demonstrate adaptive evolution in naturally complex communities is unknown. We subjected natural phytoplankton communities to three types of resource limitation (nitrogen, phosphorus, light) in outdoor mesocosms over ten weeks. We examined the community composition weekly and isolated 21 phytoplankton strains from seven species to quantify responses to selection of R* for these resources. We investigated evolutionary change in R*s in the dominant species, Desmodesmus armatus. R*s were good predictors of species changes in relative abundance, though this was largely driven by the success of D. armatus across several treatments. This species also demonstrated evolutionary change in R*s under resource limitation, supporting the potential for adaptive trait change to modify competitive outcomes in natural communities.

opencc-zeroAug 2022View details →

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Ecological determinants of variation in phenotypic selection on quantitative immune defence traits

Immune defence is an important determinant of organismal fitness. While theoretical models based on trade-offs in resource allocation predict quantitative immune traits to be subject to stabilizing selection due to associated energetic costs and self-harm, empirical studies report mainly positive directional selection. This discrepancy may arise from multiple ecological factors that vary in nature and could influence selection. We examined if selection on immune activity varies depending on immune challenge/infection risk, between immune traits, and among populations in the freshwater snail Lymnaea stagnalis. We assessed selection on the phenoloxidase-like and antibacterial activity of snail haemolymph while manipulating the level of immune challenge imposed by environmental microbes. We did this using snails from multiple populations and also quantified within-population family-level variation (i.e., evolutionary potential) in the snails' immune activity. We found that the strength of immune challenge and the examined immune trait determined selection on the snails' immune function. Thus, variation in infection risk can be an important factor in maintaining genetic variation in defence traits. Additionally, immune traits showed low among-population differentiation but high within-population genetic variation. This pattern could arise if natural snail populations are exposed to higher temporal than spatial variation in infection risk.

opencc-zeroOct 2022View details →

zenodo36/100

Integrating Local and Traditional Ecological Knowledge into Anadromous Waters Cataloging and Fish Inventories of select drainages of the Tanana and Yukon rivers 2021-2023

***Funded by the Alaska Sustainable Salmon Fund #54007, a part of the Pacific Coastal Salmon Recovery Fund Synopsis During 2021 and 2022, staff from the Alaska Department of Fish and Game (ADF&G), Division of Sport Fish, Alaska Freshwater Fish Inventory (AFFI) program and the Yukon River Drainage Fisheries Association (YRDFA) will collaborate to integrate Local and Traditional Ecological Knowledge (LTK) ethnographic interviews into a rapid systematic inventory of fish communities and associated habitats in select drainages of the lower Tanana River and Upper Yukon River in the area of Tanana and Fairbanks. First, in 2021, LTK surveys in the communities of Tanana, Manley Hot Springs and Nenana will locate important subsistence areas that will be overlain on our GIS-selected target streams to assist in filling gaps in coverage of the State of Alaska's Catalog of Waters Important for the Spawning, Rearing or Migration of Anadromous Fishes (AWC) in freshwater habitats expected to support anadromous fish populations likely to be impacted by human activities. Then, in 2022, this project will seasonally sample target streams and record observations in the Alaska Freshwater Fish Inventory database (AFFID), nominate water bodies to the AWC when anadromous fish are observed, and provide publicly available data via the AFFID internet mapping service. Anticipated benefits of this project are multiple hundreds of kilometers and/or dozens of water bodies added to the AWC as well as a broader understanding of the importance of this region’s fish species to local human communities. 1.      Introduction In Alaska, habitats that support migrating, spawning, or rearing anadromous fish are protected under multiple administrative jurisdictions, including state, federal, and local habitat protection standards. Alaska Statute (AS) 16.05.871 (the Anadromous Fish Act) is a keystone statutory protection for freshwater habitats of anadromous fish in Alaska, requiring the ADF&G to "specify the various rivers, lakes, and streams or parts of them" of the state that are important to the spawning, rearing, or migration of anadromous fish.  The resulting atlas is known as the Anadromous Waters Catalog (AWC) which is adopted as regulation under 5 AAC 95.011. Under the Anadromous Fish Act, activities and uses conducted in or otherwise affecting water bodies specified in the AWC require permitting from the ADF&G Habitat Section. Many other federal, state, and local government policies specify additional protections for anadromous fish habitat in Alaska. To be listed in the AWC, water bodies must have site-specific, direct, unambiguous observations of anadromous fish by a qualified observer. This is a major reason the AFFI program targets areas with high potential to add water bodies to the AWC. Beginning in spring 2021, YRDFA and AFFI staff will conduct LTK interviews and mapping in the communities of Tanana, Manley Hot Springs, and Nenana. By spring 2022, the LTK contributions will be mapped and added to our site selection criteria prior to field work. Based on seasonality of some fishes in this area, we will establish certain seasonal site locations that are road accessible to determine spatiotemporal patterns in the fish community used by area residents. This will include target streams sampled in June, the main summer season (see following paragraph), and September. From July 10 to August 1, 2022, 4 crews, each with 2 members, will sample fish communities using AFFI protocols in selected streams draining into the Tanana and Yukon rivers within a general area upstream of the Kokrines (a historical settlement downstream of Tanana) and downstream of the city of Fairbanks. Target sites will include wadeable headwater streams and un-wadeable streams. Summer surveys will maximize detection of juvenile and spawning Chinook salmon, juvenile coho salmon, as well as spawning summer chum salmon. More opportunistic seasonal sampling for 5 days, tentatively in late-spring (e.g., early June) and fall (September or October), could enhance the likelihood of detecting multiple life history stages of rearing, migrating, or spawning whitefishes, Chinook salmon, coho salmon, and chum salmon.  Given the size and remoteness of the Yukon and Tanana river drainages, this AFFI proposal is for years 3 and 4 of a multiyear effort to sample the region and provides enough funding to conduct spring, summer, and fall sampling. AFFI staff will pursue additional funding sources to conduct more surveys if possible. Before this proposed study, AKSSF funded AFFI to survey the upper Yukon and Tanana River drainages in 2019 and 2020 (AKSSF projects 44375 and 53013, respectively). For example, 2019 surveys in the upper Yukon and Tanana river drainages documented >40 streams previously unlisted in the AWC for Chinook salmon. 2.      Location(s) Sampling will be done in select drainages of the Yukon and Tanana rivers bounded downstream near the old Yukon River village of Kokrines (N 64.9376, W -154.6944) and upstream to the Tanana River tributary Willow Creek (N 64.6719, W -148.2027). This includes the area and tributaries around the confluence of the Yukon and Tanana rivers (N 65.1682, W -151.9982) between the villages of Tanana and Manley Hot Springs. I.                   Objectives Objective 1: To maximize the spatial increase of documented anadromous fish habitats depicted in the AWC within the study area (sampling a minimum 80 headwater target streams, and 12 un-wadeable target streams) not including repeat sampling of select sites to document seasonal presence of some anadromous species. Objective 2: To use LTK to maximize the spatial increase of documented anadromous fish habitats depicted in the AWC within the study area while also corroborating and verifying the LTK with field surveys. Objective 3:  To record characteristics, using established protocols, of aquatic habitats (including riparian zone) at each sampling location. Objective 4:  To provide the fish distribution and associated aquatic habitat information to State & Federal agencies, participating communities, and the public. II.                Methods This collaborative project is designed to contribute to the AWC using social and biological methods. Prior to field work, a YRDFA anthropologist and ADF&G staff will contact the Tribal Councils of Tanana, Manley Hot Springs, and Nenana to schedule community meetings (in-person or online, as able) and ethnographic interviews between late spring 2021 and spring 2022. These interviews and mapping activities will establish what is known about the timing and distribution of resident and anadromous fishes and create maps that can be overlain on the AWC with other AFFI site selection criteria to identify streams to sample the following year. The next year, project staff will seek to verify LTK surveys and add to the AWC through seasonal sampling. The proposed study area for 2020 has a road system along the Tanana River which will allow access via truck and boat to certain streams during 5 days each in spring (June) and fall (September). This will likely raise the number of sites this project can sample while avoiding excess helicopter expenses. Additionally, this will allow better seasonal sampling efforts to maximize the ability to document seasonally variable fish distributions such as summer salmon spawning and fall whitefish spawning seasons. Summer sampling will be more expansive and follow ADF&G's AFFI protocols (Giefer and Cathcart 2019) where 4 crews, each with 2 members, will use helicopters to sample fish communities in selected study stream reaches for approximately 21 days in summer of 2022. Target survey sites will include wadeable headwater streams sampled with a backpack electrofisher, and un-wadeable streams sampled with a raft-mounted electrofisher. Sites within the study area that are identified as being anadromous fish rearing from LTK surveys and currently unlisted in the AWC will be prioritized for verification.           Study area selection The long-term goal of the AFFI program is to complete a statewide baseline inventory of fish assemblages and associated aquatic and riparian habitats. At its inception, the AFFI program developed a systematic approach to rank and prioritize Alaska’s 139 subbasin level hydrologic units. At the time of this proposal, the AFFI program has surveyed 81 of the 139 subbasins that were originally prioritized. This project’s 99,099 square kilometer study area includes subbasins of the lower Tanana River between the city Fairbanks and the mouth of the Tanana River, tributaries draining the south side of the Tanana upstream of Fairbanks but west of Clear Creek, and in select subbasins of the Yukon River near the community of Tanana but upstream of Kokrines.  Target stream selection Target stream selection will be performed by integrating LTK survey information with our conventional method of using GIS to identify previously unsampled (or not rigorously sampled) streams that can be safely accessed while maximizing potential additions to the AWC. The number of headwater streams in the study area will exceed the project’s limited sampling effort capacity; therefore, a subset of streams comprising the longest stream segments not listed in the AWC will be selected as targets. The headwater team will sample approximately six to eight headwater streams per day and, when operating, the raft or riverboat team will float and sample one un-wadeable stream per day. Based on past AFFI projects, it is estimated that a minimum of 80 headwater target streams will be sampled, and 12 un-wadeable target streams could be rafted and sampled during the 21 field days (not including the 5 field days in each of June and September).  However, these estimates are contingent upon weather and logistics. Reference sites for seasonal sampling will be prioritized depending on spatial and temporal observations from LTK surveys where we will select road or boat accessible locations to target fishes in spring, summer, and fall. We will seek to access all LTK-identified subbasins for subsistence fishes but they will be prioritized according to logistics (i.e., fuel and time needed to reach location) and potential addition to the AWC. Sampling methods Ideally, the fish community and habitat will be sampled with standardized methods per AFFI protocols. Fish will be collected by single-pass electrofishing standardized by stream width (i.e., 40 or 120 wetted-channel-widths in wadeable and un-wadeable target streams, respectively). Captured fish will be identified, measured, and released. Other gear types (such as beach seines, angling, or minnow traps) may be deployed if conditions prohibit electrofishing. Standard water chemistry, channel morphology, and riparian habitat parameters will be recorded at each sample site in addition to longer-term water temperature or eDNA sampling efforts in reference streams.   III.             Benefits Updated and more comprehensive AWC coverage will be the primary regulatory or fish habitat benefit of this project toward sustaining salmon habitat. Enhanced communication and partnerships with tribal communities will be established through interviews to gather LTK. Based on summer AFFI sampling since 2016, sampling at least 80 headwater target streams and 12 un-wadeable target streams, this project will add many (likely >300) previously unlisted kilometers of salmon habitat among several distinct streams to the AWC. Only anadromous fish habitat listed in the AWC receives protection under the Anadromous Fish Act and various other policies that provide additional protections to specified anadromous fish habitat. Also, providing more complete (e.g., seasonal) and accessible fish community and habitat information will benefit ADF&G, as well as help other federal, state, and local resource agencies better implement their respective fish habitat management, protection, and research missions.  Better protection and management of salmon habitat will benefit salmon fisheries and the communities they sustain by safeguarding critical salmon habitat thereby ensuring the long-term productivity of habitats and salmon populations.

opencc-by-4.0Oct 2024View details →

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The evolution of sexually dimorphic traits in ecological gradients: An interplay between natural and sexual selection in hummingbirds

Traits that exhibit differences between the sexes have been of special interest in the study of phenotypic evolution. Classic hypotheses explain sexually dimorphic traits via intrasexual competition and mate selection, yet natural selection may also act differentially on the sexes to produce dimorphism. Natural selection can act either through physiological and ecological constraints on one of the sexes or by modulating the strength of sexual/social selection. This predicts an association between the degree of dimorphism and variation in ecological environments. Here, we characterise the variation in hummingbird dimorphism across ecological gradients using rich databases of morphology, colouration, and song. We show that morphological dimorphism decreases with elevation in the understorey and increases with elevation in mixed habitats, that dichromatism increases at high altitudes in open and mixed habitats, and that song is less complex in mixed habitats. Our results are consistent with flight constraints, lower predation pressure at high elevations, and with habitat effects on song transmission. We also show that dichromatism and song complexity are positively associated, while tail dimorphism and song complexity are negatively associated. Our results demonstrate that key ecological factors shape sexually dimorphic traits and that different communication modalities do not always evolve in tandem.

opencc-zeroOct 2022View details →

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