9564

• UCREFRP Catalog Number: 9564
• Author: Olden, J. D., N. L. Poff and K. R. Bestgen
• Title: Trait Synergisms and the Rarity, Extirpation, and Extinction Risk of Desert Fishes
• USFW Year: 2008
• USFW - Doc Type: Ecology
• Copyright Material: YES

March 2008 EXTINCTION-PRONE TRAITS OF DESERT FISHES
0
w 10
N 6
I
ca 2 i
Z L ME MI HE Hl
a
a)
.v
Lei
0
Z
I
Maximum body length - 95.0 cm
Yac No
10
4
s L
2
1
o L ME MI HE HI
#
c L ME Ml HE Hl
853
A
I Maximum body length = 9.6 cm 1
ra Yes _ 6 li Nn
m 4
a 2 2
0 - 0 ?n -
Z L ME Ml HE HI L ME MI HE HI
B Yes - ..""I?
( n guarder Parental care g t.5 2 No
m open substrate) (reproductive guild) (all others)
U
CL 2
Z L ME MI HE HI L ME MI HE HI
All Trophic guild Herbivore/
? others I detri#ivore
v 4 4
C 2
O 0 0
Z L ME Ml HE HI L ME Ml HE HI
Swim factor :mz? 0.39
co
4 Yes 4 No
N 2 i? 2
0 0 0
Z L ME Ml HE HI L ME MI HE HI
C
D
Length at maturity =10.2 cm
(age at maturity :EE 2.5 years)
Yes (longevity :5 6.0 years) No
2 2
1 1 i
0
L ME MI HE HI L ME MI HE HI
F G
FrG. 3. Classification tree discriminating among native species of the Lower Colorado River Basin according to level and source
of threat to extinction: none/low risk (L) indicated by black bars, moderate risk (ME) and high risk (HE) from environmental
alterations indicated by white bars, and moderate risk (MI) and high risk (HI) from species invasions indicated by gray bars. In all
panels, the y-axis represents the number of species. According to the tree branching topology, we also interpret the best competitive
surrogate splits (indicated in parentheses) that showed similar classification power to the primary split. Letters A-G indicate
terminal nodes.
bimodal relationship with extinction vulnerability
whereby both small- and large-bodied native fishes were
more at risk. The same relationship is evident for the
world's freshwater fishes; globally imperiled species
exhibit a bimodal size-frequency distribution indicating
that small- and large-bodied species are relatively more
threatened (Olden et al. 2007). We found that lack of
parental care and specialized feeding behavior also were
associated with elevated extinction risk, but their effects
were only apparent for intermediate body sizes. These
results suggest that the manner in which species traits
are related to the extinction risk of Lower Colorado
River fishes is both complex and sensitive to other life-
history attributes, including body size. Broader support
for this finding comes from Cardillo et al. (2005) who
showed that the relationship between extinction risk of
mammals and life-history traits varies as a function of
body size.
By partitioning overall extinction risk according to
different sources of threat, we improved our under-
standing of the linkages between fish species traits and
specific drivers of environmental change in the Lower
Colorado River Basin. An important finding was that
species under threat to environmental alteration are
characterized by body morphologies indicative of
weaker swimming ability (and potentially poor dispersal