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Browett SS, Synnott R, O'Meara DB, Antwis RE, Browett SS, Bown KJ, Wangensteen OS, Dawson DA, Searle JB, Yearsley JM, McDevitt AD. Resource competition drives an invasion-replacement event among shrew species on an island. J Anim Ecol 2023; 92:698-709. [PMID: 36617677 DOI: 10.1111/1365-2656.13855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 11/17/2022] [Indexed: 01/10/2023]
Abstract
Invasive mammals are responsible for the majority of native species extinctions on islands. While most of these extinction events will be due to novel interactions between species (e.g. exotic predators and naive prey), it is more unusual to find incidences where a newly invasive species causes the decline/extinction of a native species on an island when they normally coexist elsewhere in their overlapping mainland ranges. We investigated if resource competition between two insectivorous small mammals was playing a significant role in the rapid replacement of the native pygmy shrew Sorex minutus in the presence of the recently invading greater white-toothed shrew Crocidura russula on the island of Ireland. We used DNA metabarcoding of gut contents from >300 individuals of both species to determine each species' diet and measured the body size (weight and length) during different stages of the invasion in Ireland (before, during and after the species come into contact with one another) and on a French island where both species have long coexisted (acting as a natural 'control' site). Dietary composition, niche width and overlap and body size were compared in these different stages. The body size of the invasive C. russula and composition of its diet changes between when it first invades an area and after it becomes established. During the initial stages of the invasion, individual shrews are larger and consume larger sized invertebrate prey species. During later stages of the invasion, C. russula switches to consuming smaller prey taxa that are more essential for the native species. As a result, the level of interspecific dietary overlap increases from between 11% and 14% when they first come into contact with each other to between 39% and 46% after the invasion. Here we show that an invasive species can quickly alter its dietary niche in a new environment, ultimately causing the replacement of a native species. In addition, the invasive shrew could also be potentially exhausting local resources of larger invertebrate species. These subsequent changes in terrestrial invertebrate communities could have severe impacts further downstream on ecosystem functioning and services.
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Affiliation(s)
- Samuel S Browett
- School of Science, Engineering and Environment, University of Salford, Salford, UK.,Molecular Ecology Research Group, Eco-Innovation Research Centre, School of Science and Computing, South East Technological University, Waterford, Ireland.,NERC Environmental Omics Facility, School of Biosciences, University of Sheffield, Sheffield, UK
| | - Rebecca Synnott
- Molecular Ecology Research Group, Eco-Innovation Research Centre, School of Science and Computing, South East Technological University, Waterford, Ireland
| | - Denise B O'Meara
- Molecular Ecology Research Group, Eco-Innovation Research Centre, School of Science and Computing, South East Technological University, Waterford, Ireland
| | - Rachael E Antwis
- School of Science, Engineering and Environment, University of Salford, Salford, UK
| | - Stephen S Browett
- School of Science, Engineering and Environment, University of Salford, Salford, UK
| | - Kevin J Bown
- School of Science, Engineering and Environment, University of Salford, Salford, UK
| | - Owen S Wangensteen
- Norwegian College of Fishery Science, University of Tromsø, Tromsø, Norway
| | - Deborah A Dawson
- NERC Environmental Omics Facility, School of Biosciences, University of Sheffield, Sheffield, UK
| | - Jeremy B Searle
- Department of Ecology and Evolution, Corson Hall, Cornell University, Ithaca, New York, USA
| | - Jon M Yearsley
- School of Biology and Environmental Science, University College Dublin, Dublin, Ireland
| | - Allan D McDevitt
- School of Science, Engineering and Environment, University of Salford, Salford, UK.,Department of Natural Sciences and the Environment, School of Science and Computing, Atlantic Technological University, Galway, Ireland
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Fletcher LS, Bolander M, Reese TC, Asay EG, Pinkston E, Griffen BD. Metabolic rates of the Asian shore crab Hemigrapsus sanguineus in air as a function of body size, location, and injury. Ecol Evol 2022; 12:e9297. [PMID: 36177136 PMCID: PMC9463042 DOI: 10.1002/ece3.9297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 08/18/2022] [Accepted: 08/25/2022] [Indexed: 11/07/2022] Open
Abstract
Rapid warming in the Gulf of Maine may influence the success or invasiveness of the Asian shore crab, Hemigrapsus sanguineus. To better predict the effects of climate change on this invasive species, it is necessary to measure its energy dynamics under a range of conditions. However, previous research has only focused on the metabolism of this intertidal species in water. We sampled adult crabs from three different sites and measured their metabolic rates in the air. We show that metabolic rate increases with body mass and the number of missing limbs, but decreases with the number of regenerating limbs, possibly reflecting the timing of energy allocation to limb regeneration. Importantly, metabolic rates measured here in the air are ~4× higher than metabolic rates previously measured for this species in water. Our results provide baseline measurements of aerial metabolic rates across body sizes, which may be affected by climate change. With a better understanding of respiration in H. sanguineus, we can make more informed predictions about the combined effects of climate change and invasive species on the northeast coasts of North America.
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Affiliation(s)
| | | | | | | | - Emily Pinkston
- Department of BiologyBrigham Young UniversityProvoUtahUSA
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Predicting invasive consumer impact via the comparative functional response approach: linking application to ecological theory. Biol Invasions 2022. [DOI: 10.1007/s10530-022-02862-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
AbstractThe Comparative Functional Response Approach (CFRA) was developed to provide a practical methodology by which short-term experiments can be used to forecast the longer-term impacts of a potential invading consumer. The CFRA makes inferences about potential invader impact based on comparisons of the functional responses of invader and native consumers on native resources in a common experimental venue. Application of the CFRA and derivative approaches have proliferated since it was introduced in 2014. Here we examine the conceptual foundations of the CFRA within the context of basic Lotka–Volterra consumer-resource theory. Our goals are to assess whether core predictions of the CFRA hold within this framework, to consider the relative importance of background mortality and consumer assimilation efficiency in determining predator impact, and to leverage this conceptual framework to expand the discussion regarding stability and long term consumer and resource dynamics. The CFRA assertion that consumers with a higher functional response will have larger impacts on resources only holds as long as all other parameters are equal, but basic theory indicates that predator impacts on prey abundance and stability will depend more on variation in conversion efficiency and background mortality. While examination of the CFRA within this framework highlights limitations about its current application, it also points to potential strengths that are only revealed when a theoretical context is identified, in this case the implications for stability and conceptual links to competition theory.
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Potter B, Cannizzo ZJ, Griffen BD. Morphometric correlations between dietary and reproductive traits of two brachyuran crabs, Hemigrapsus sanguineus and Aratus pisonii. PLoS One 2022; 17:e0267369. [PMID: 35925929 PMCID: PMC9352013 DOI: 10.1371/journal.pone.0267369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 07/19/2022] [Indexed: 11/18/2022] Open
Abstract
Many animals have flexible morphological traits that allow them to succeed in differing circumstances with differing diets available to them. For brachyuran crabs, claw height and gut size are diet-specific and largely reflect foraging strategies, while abdomen width reflects relative levels of fecundity. However, the link between claw size and diet has largely been documented only for primarily carnivorous crabs, while the link between diet and fecundity is strong in herbivorous crabs. We sought to determine the nature of the intraspecific relationship between claw size, dietary habits, and fecundity for two primarily herbivorous crab species, Hemigrapsus sanguineus and Aratus pisonii. Specifically, we examined whether claw size and/or abdomen width can be used as reliable measures of individual diet strategy. To test these hypotheses, we collected crabs and measured the dimensions of their claws, abdomens, and guts. By comparing these dimensions for each individual, we found that strongly predictive relationships do not exist between these traits for the primarily herbivorous species in our study. Thus, identifying external morphological features that can be used to assess diets of primarily herbivorous crabs remains elusive.
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Affiliation(s)
- Ben Potter
- Biology Department, Brigham Young University, Provo, UT, United States of America
| | - Zachary J. Cannizzo
- National Oceanic and Atmospheric Administration Office of National Marine Sanctuaries − National Marine Protected Areas Center, Silver Spring, MD, United States of America
| | - Blaine D. Griffen
- Biology Department, Brigham Young University, Provo, UT, United States of America
- * E-mail:
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Griffen BD. Considerations When Applying the Consumer Functional Response Measured Under Artificial Conditions. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.713147] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Since its creation, considerable effort has been given to improving the utility of the consumer functional response. To date, the majority of efforts have focused on improving mathematical formulation in order to include additional ecological processes and constraints, or have focused on improving the statistical analysis of the functional response to enhance rigor and to more accurately match experimental designs used to measure the functional response. In contrast, relatively little attention has been given to improving the interpretation of functional response empirical results, or to clarifying the implementation and extrapolation of empirical measurements to more realistic field conditions. In this paper I explore three concepts related to the interpretation and extrapolation of empirically measured functional responses. First, I highlight the need for a mechanistic understanding when interpreting foraging patterns and highlight pitfalls that can occur when we lack understanding between the shape of the functional response curve and the mechanisms that give rise to that shape. Second, I discuss differences between experimental and real-world field conditions that must be considered when trying to extrapolate measured functional responses to more natural conditions. Third, I examine the importance of the time scale of empirical measurements, and the need to consider tradeoffs that alter or limit foraging decisions under natural conditions. Clearly accounting for these three conceptual areas when measuring functional responses and when interpreting and attempting to extrapolate empirically measured functional responses will lead to more accurate estimates of consumer impacts under natural field conditions, and will improve the utility of the functional response as a heuristic tool in ecology.
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