Beyond taxonomy: A traits-based approach to fish community ecology
Beyond taxonomy: A traits-‐based approach to ﬁsh community ecology Julian D. Olden School of Aqua,c and Fishery Sciences University of Washington firstname.lastname@example.org
Big Fish Eat Li,le Fish by Pieter Brueghel the Elder (1557)
Threats to Freshwater Fishes Habitat loss PollutionFragmentation Climate changeInvasive speciesDisease
Why Trait-‐based Ecology? • Enhances our mechanis,c understanding of ecological paHern and process • Provides greater opportunity for generaliza,on • Links biodiversity and ecosystem func,on
Traits in Fish Community Ecology • The study of ﬁsh traits can be used to understand complex phenomena, including why organisms live where they do, how many species can coexist in a given place, and how they will respond to environmental change 0 20 40 60 80 100 120 1991 1994 1997 2000 2003 2006 2009 2012 # publicaFons ISI Web of Science search on Jan 20, 2013 using the query “ﬁsh AND trait* AND (community OR assemblage)”
Research PrioriFes “In an ideal world, an understanding of how ﬁsh assemblages change in response to natural changes along diﬀerent ,me scales would be necessary … This is no longer always possible, however, since most aqua,c environments are already subject to some form of human interven,on … Therefore, it is necessary to deal with mixed signals, and part of the challenge lies in numerically dis,nguishing these signals, as well as pucng them in perspec,ve.”
Today’s PresentaFon 1. Do species traits provide predic,ve insight into those ﬁsh species at greatest risk to ex,nc,on? 2. Does a traits-‐based approach represent a unifying framework for an,cipa,ng how ﬁsh species and communi,es will response to environmental change? Biodiversity and Ecosystem Func,oning Ex,nc,on Invasion
1. ExFncFon Risk of Fishes • Conserva,on biology is faced with a growing urgency to iden,fy and protect species facing the greatest risk of ex,nc,on (Pimm and Jenkins 2005) • This is a challenging task because direct es,mates of ex,nc,on risk for most species are lacking (O’Grady et al. 2004) • Ecological traits can help iden,fy species that are vulnerable to ex,nc,on
Body Size and Global ExFncFon Risk • Body size is a fundamental ecological parameter correlated with many other life-‐history characteris,cs • Ecological theory and global-‐scale analyses of bird and mammal faunas suggest that small-‐bodied species are less vulnerable to ex,nc,on • We compared body-‐size distribu,ons of 22,800 freshwater and marine ﬁshes under diﬀerent levels of global ex,nc,on risk
YES. Dip sta,s,c = 0.12, d.f. = 14, P = 0.042 NO. Dip sta,s,c = 0.07, d.f. = 16, P = 0.889 Olden, J.D., Hogan, Z.S., and M.J. Vander Zanden. 2007. Small ﬁsh, big ﬁsh, red ﬁsh, blue ﬁsh: size-‐biased ex,nc,on risk of the world’s freshwater and marine ﬁshes. Global Ecology and Biogeography 16:694-‐701. Is the distribu,on signiﬁcantly bi-‐modal?
ImplicaFons • Given limited resources for conduc,ng detailed species assessments, iden,fying trait-‐based indicators of ex,nc,on risk could be extremely valuable for conserva,on ranking schemes • Traits may provide insight into the ecosystem implica,ons of species losses (and invasions) Castello et al., in press. The vulnerability of Amazon freshwater ecosystems. Conserva;on Le,ers.
2. Life-‐histories and the habitat templet Trade-‐oﬀs among energeFc investments in growth, reproducFon, and survivorship have resulted in the evoluFon of life history strategies that enable an organism to cope with ecological challenges Southwood (1988)
Fish Life-‐history Theory • Life history theory has sparked new perspec,ves in understanding the paHerns and drivers of freshwater biodiversity Olden & Kennard (2010) • Life-‐history strategies have evolved from trade-‐oﬀs among traits that have direct consequences for ﬁtness in diﬀerent environments (Winemiller and Rose 1992) Fecundity
Fish Life-‐history Theory Fecundity OPPORTUNISTIC • small • rapidly matura,on • low fecundity • unpredictable env. PERIODIC • large • late matura,on • high fecundity • seasonal env. EQUILIBRIUM • medium • low fecundity • ↑parental care • constant env.
OpportunisFc Periodic Equilibrium Life-‐histories of North American ﬁshes Mims, M.C., Olden, J.D., ShaHuck, Z.R., and N.L. Poﬀ. 2010. Life history trait diversity of na,ve freshwater ﬁshes in North America. Ecology of Freshwater Fish 19:390-‐400.
• It is hypothesized that a species’ life history strategy dictates, in large part, its response to environmental factors describing the variability, predictability, and seasonality of favorable habitat condi,ons Modiﬁed from Bunn and Arthington (2002, Env. Man.)
• Hydrological variability plays a dominant role in shaping physical processes in riverine ecosystems, and a number of recent studies have supported the associa,on between hydrology and ﬁsh life history strategies
ObjecFve Test life history theory by quan,fying rela,onships between variability, predictability, and seasonality of natural ﬂow regimes and the life history composi,on of na,ve ﬁsh assemblages throughout the con,nental United States.
Approach >15 years con,nuous gage data prior to ﬁsh survey? Gage-‐survey pair within 10 river km? Any tributaries between the pair? YES YES NO Acceptable pair (n=109) Flow Gages Fish Surveys
Approach • Assign each ﬁsh species to a life history strategy and calculate rela,ve strategy richness for each site • Calculate hydrologic metrics that summarize the major components of the ﬂow regime Predictability Variability Seasonality
PredicFons from Life History Theory Flow dimension Hydrologic metric Predicted relaFonship with proporFonal LH (slope direcFon) OpportunisFc Periodic Equilibrium VARIABILITY Annual Coef. Varia,on + -‐ -‐ High Pulse Count + -‐ -‐ PREDICTABILITY Base Flow Index -‐ 0 + Flow Predictability -‐ + + SEASONALITY Constancy/Predictability 0 -‐ + High Pulse Dura,on -‐ + 0 Used quan,le regression to test for rela,onships between LHs and hydrologic metrics
• The majority (two-‐thirds) of rela,onships were sta,s,cally signiﬁcant (P<0.05) for at least one quan,le • 82% of signiﬁcant rela,onships supported predic,ons from life history theory Opp Per Equ Mims, M.C., and J.D. Olden. 2012. Life history theory predicts streamﬂow eﬀects on ﬁsh assemblage response to hydrologic regimes. Ecology 93:35-‐45.
• The majority (two-‐thirds) of rela,onships were sta,s,cally signiﬁcant (P<0.05) for at least one quan,le • 82% of signiﬁcant rela,onships supported predic,ons from life history theory Opp Per Equ Mims, M.C., and J.D. Olden. 2012. Life history theory predicts streamﬂow eﬀects on ﬁsh assemblage response to hydrologic regimes. Ecology 93:35-‐45. Flow Variability
• The majority (two-‐thirds) of rela,onships were sta,s,cally signiﬁcant (P<0.05) for at least one quan,le • 82% of signiﬁcant rela,onships supported predic,ons from life history theory Mims, M.C., and J.D. Olden. 2012. Life history theory predicts streamﬂow eﬀects on ﬁsh assemblage response to hydrologic regimes. Ecology 93:35-‐45. Flow Seasonality
Flow dimension Hydrologic metric Predicted relaFonship with proporFonal LH (slope direcFon) OpportunisFc Periodic Equilibrium VARIABILITY Annual Coef. Varia,on + -‐ -‐ High Pulse Count + -‐ -‐ PREDICTABILITY Base Flow Index -‐ 0 + Flow Predictability -‐ + + SEASONALITY Constancy/Predictability 0 -‐ + High Pulse Dura,on -‐ + 0 = Supported by theory = Inconclusive = Not support by theory Life history theory predicts ﬁsh assemblage response to hydrologic regimes
ImplicaFons • The ﬂow regime as a key determinant of ﬁsh life history composi,on across a broad biogeographical scale • A traits-‐based approach is useful because it facilitates the transfer of scien,ﬁc knowledge between regions that naturally diﬀer due to zoogeography, but in which life history strategies and trait adapta,ons are hypothesized to converge across diverse taxonomies • These ﬁndings have implica,ons for predic,ng the consequences of ﬂow altera,on and for informing ﬂow-‐management recommenda,ons
• Fish life-‐history strategies are predic,ve of how ﬁsh assemblages response to damming and altered ﬂow regimes Mims, M.C., and J.D. Olden. 2013. Fish assemblages respond to altered ﬂow regimes via ecological ﬁltering of life history strategies. Freshwater Biology 58:50-‐62.
Key Challenges Does a trait-‐based approach provide new insight into paHerns and processes of ﬁsh biogeography, and if so, can this informa,on inform conserva,on strategies? What traits predispose ﬁsh species to ex,nc,on vs. invasion? Given the lack of trait data for many ﬁsh species in par,cular regions, which subset of traits are most appropriate for deﬁning func,onal diversity and oﬀer the most promise for predic,ng responses to environmental change? What are the ecosystem consequences of changes in ﬁsh func,onal composi,on?
PredicFng ExFncFon Risk “More appropriate biological knowledge is s;ll required to improve species assignment to the IUCN Red List categories at the regional level” Transferring Knowledge “One of the major problems facing ﬁsh conserva;on in South America is the lack of basin-‐wide approaches. Usually, both knowledge and interest are limited to the local …”
Julian D. Olden University of Washington email@example.com Special thanks to Meryl Mims!