Transcript PowerPoint Example 1

Evolutionary potential in Carex lutea (Cyperaceae), a rare North American endemic
Akanita Sangaumphai, Nathan Derieg, Jackie Campbell, and Leo P. Bruederle
Department of Biology, University of Colorado at Denver and Health Sciences Center, Denver, CO 80217
Introduction
Materials and Methods
The evolutionary potential of a species is correlated with the levels of genetic
diversity maintained within and among populations. Carex lutea LeBlond
(Cyperaceae) is a narrow endemic, restricted in distribution to approximately
eight populations in Pender and Onslow Counties, North Carolina (Fig. 1-2). It
was first described in 1994 from the Atlantic Coastal Plain, where it occupies
wet sandy soils underlain by coquina limestone in rare wet savannas. Its
closest relatives include C. cryptolepis Mack., a broadly distributed North
American endemic, and the widespread C. flava L., within section Ceratocystis.
Soluble enzymatic proteins were extracted from leaf tissue (Bruederle and
Fairbrothers, 1986) harvested from a total of 161 individuals of C. lutea
collected “haphazardly” at five sites (N=13-50), as well as 322 individuals of C.
cryptolepis representing ten sites (N=19-50) (Table 1). Extracts were stored at 70o until separation, which involved each of three starch gel and electrode
buffer systems (Kuchel and Bruederle, 2000). Following electrophoresis,
substrate-specific stains were used to visualize allozymes. Data were collected
as genotypes for each individual at 19 putative loci , e.g., AAT, and analyzed to
obtain common measures of genetic diversity, e.g., P and He, and structure,
e.g., FST using GDA (Lewis and Zaykin, 2002).
Although expected to exhibit relatively low levels of genetic diversity, in general,
endemics have proven to be unpredictable. Carex lutea, with its restricted
distribution; small, isolated populations; habitat specificity; and caespitose habit
was anticipated to meet expectations of low genetic diversity.
The objective of this research was to describe genetic diversity and its
apportionment within and among populations of C. lutea, a Federally listed
endangered species. For comparative purposes, we enlist C. cryptolepis.
Carex lutea
C. cryptolepis
Site
Haws Run Savanna
Neck Savanna
Sandy Run Savanna
Shaken Creek Savanna
Watkins Savanna
Cambridge
Muck Lake
Aldrich Lake
Dow Lake
Pointe aux Chenes R.
Tuttle Marsh
Ankeney Fen
Springville Marsh
Sayles Rd.
Tyler Pond
N
41
23
13
45
39
19
50
50
25
25
28
26
50
25
25
County
Pender Co.
Pender Co.
Onslow
Pender Co.
Pender Co.
State
NC
NC
NC
NC
NC
Dane Co.
Douglas Co.
Schoolcraft Co.
Emmet Co.
Mackinac Co.
Iosco Co.
Greene Co.
Seneca Co.
St. Lawrence Co.
Kennebec Co.
WI
WI
MI
MI
MI
MI
OH
OH
NY
ME
Latitude
unavailable
unavailable
unavailable
unavailable
unavailable
43º 00' 18"N
46º 23' 32"N
46º 07' 39"N
45º 42' 23"N
45º 57' 11"N
44º 23' 45"N
39º 44' 48"N
41º 00' 24"N
44º 38' 10"N
44º 23' 42"N
Longitude
unavailable
unavailable
unavailable
unavailable
unavailable
89º 01' 10"W
91º 33' 12"W
86º 13' 08"W
84º 43' 58"W
84º 52' 23"W
83º 25' 17"W
83º 59' 32"W
83º 24' 04"W
74º 56' 10"W
69º 49' 24"W
Table 1. Locations for five Carex lutea and ten C. cryptolepis populations sampled
for allozyme analysis, where N equals number of individuals sampled.
Results
Seven loci were polymorphic in C. lutea: AAT, ADH, DIA-1, G3PDH, IDH-2,
PGM-1, and SOD; while C. cryptolepis was polymorphic at eight loci: DIA-1,
IDH-1, IDH-2, MDH-2, ME, PGI-2, PGM-1, and SDH (Table 2).
Fig. 1. Habit for (a) Carex lutea (www.herbarium.unc.edu) and (b) C. cryptolepis
(www.botany.wisc.edu/herbarium).
a
Although total genetic diversity was low, (e.g., HT=0.078), populations of C.
lutea harbored levels of diversity that were significantly higher than C. cryptolepis, as well as averages reported for other caespitose carices (Bruederle,
Yarbrough, and Kuchel, in press). For example, proportion of loci polymorphic
(P) averaged across populations was 20.0% in C. lutea, 6.3% in C. cryptolepis,
and 14.2% for other caespitose carices. However, C. lutea showed similar
reductions in heterozygosity from expectations (He = 0.048 and Ho = 0.026),
presumably due to inbreeding within populations. FIS – reduction in heterozygosity due to inbreeding – averaged 0.457 (Table 3).
Population differentiation in C. lutea (FST = 0.411, 95% CI 0.047-0.498) was
similar to that reported for other caespitose carices, but significantly less than
that observed for C. cryptolepis (FST = 0.789, 95% CI 0.597-0.941).
Species
Carex lutea
b
Fig. 2. Distribution of (a) Carex lutea (http://quickfacts.census.gov) and (b) C.
cryptolepis (modified from Crins and Ball, 1988;).
Site
Haws Run
Neck Savanna
Sandy Run Savanna
Shaken Creek Savanna
Watkins Savanna
mean
C. cryptolepis
mean
caespitose carices mean
P
31.6%
15.8%
10.5%
21.1%
21.1%
20.0%
P.05
26.3%
10.5%
10.5%
10.5%
15.8%
14.7%
6.3% 3.7%
14.2% na
Ap
2.2
2.3
2.0
2.0
2.3
2.2
Ho
0.057
0.017
0.022
0.013
0.024
0.026
He
0.093
0.031
0.036
0.034
0.046
0.048
2.0 0.006 0.011
2.1
na 0.043
Table 2. Summary of genetic diversity statistics in Carex lutea and C. cryptolepis.
Carex lutea
Haw's Run
Neck Savanna
Sandy Run Savanna
Shaken Creek
Watkins Savanna
C. cryptolepis
Aldrich Lake
Ankeney Fen
Cambridge
Dow Lake
Muck Lake
Pointe aux Chenes
Sayles Road
Springville
Tuttle Marsh
Tyler Pond
AAT ADH DIA-1 G3PDH IDH-2 MDH-2
0.416 0.393 0.386
**** -0.013 ****
0.472 ****
****
****
****
****
****
**** 0.290
****
****
****
-0.011 **** 0.664 0.793
****
****
0.614 ****
****
****
0.298
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
0.785
****
****
****
****
****
****
****
****
****
****
****
****
****
ME
****
****
****
****
****
PGM-1 SDH SOD
0.350
**** 0.540
0.662
****
****
0.645
****
****
****
****
****
0.528
****
****
0.814
****
****
****
****
****
****
****
****
****
****
****
****
****
****
0.589
****
**** -0.091 ****
0.566
**** -0.086 ****
****
1.000
****
****
****
****
****
****
****
****
****
-0.021 -0.021 ****
**** -0.021
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
****
Table 3. Fixation indices for ten polymorphic loci in Carex lutea and C.
cryptolepis; statistical significance (Fisher Measure) is indicated with bold.
Discussion
In contrast to expectations for a narrow endemic [e.g., Dodd and Helenurm
(2002)], populations of C. lutea exhibit levels of genetic diversity that are
significantly higher in comparison to its congener C. cryptolepis. However,
this diversity is apportioned similarly. Carex lutea and C. cryptolepis
display levels of inbreeding that are similar to other caespitose carices,
likely a consequence of habit and self-compatibility.
Typically, these species maintain a high percentage of genetic diversity as
differences among populations; this was observed both for C. lutea and C.
cryptolepis. Low levels of gene flow, coupled with large range, are likely
responsible for higher levels of population differentiation in disjunct
populations of C. cryptolepis, such as Ankeney Fen.
For C. lutea and C. cryptolepis, it appears that distribution, broad or narrow,
is not necessarily a reliable indicator of genetic diversity. Considering their
shared life history (e.g., narrow niche, caespitose habit, small population
size), we conclude that historical factors are largely responsible for the
differences reported herein. The greatest threat to C. lutea is not a
reduction in evolutionary potential (as a consequence of endemism), but
rather loss of habitat.
References
Bruederle, L.P., S.L. Yarbrough, and S.D. Kuchel. In press. Allozyme
variation in the genus Carex… 15 years later: 1986-2001. in: R. Naczi,
editor. Sedges 2002: Uses, Diversity, and Systematics. Missouri Botanic
Garden, St. Louis,
Crins, W.J., P.W. Ball. 1988. Taxonomy of the Carex flava complex
(Cyperaceae) in North America and northern Eurasia. II. Taxonomic
treatment. Can. J. Bot. 67: 1048-1065.
Dodd, S.C., and K. Helenurm. 2002. Genetic diversity in Delphinium
variegatum: a comparison of two insular endemic subspecies and their
widespread mainland relative. Amer. J. Bot. 89:613-622.
Kuchel, S.D. and L.P. Bruederle. 2000. Genetic diversity and structure in
North American populations of Carex viridula Michx. (Cyperaceae).
Madrono 47: 147-158.
Lewis, P. O., and D. Zaykin. 2001. Genetic Data Analysis: Computer
program for the analysis of allelic data. Version 1.0 (d16c).
http://lewis.eeb.uconn.edu/lewishome/software.html
Acknowledgments. We thank Richard LeBlond for field assistance;
UCDHSC Undergraduate Research Opportunity Program, Faculty Development, and Council Awards for Graduate Student Research for grant
funding; and Ron Rinkle for a generous donation supporting this research.