Preserving evolutionary potential: the role of genetic rescue Jill Hamilton North Dakota State University Genetic consequences of rarity
Genetic Demographic variation variation Inbreeding depression Population growth rate
Outbreeding depression Reproductive rates Ne Evolutionary Potential?
Environmental variation Fluctuations Disease Stress How might genetic rescue impact a species evolutionary potential? Natural or facilitated introduction of genetic variation from unrelated individuals with an aim to increase population fitness
Environmental change
Extinction threshold
(Hamilton and Miller 2016, Conservation Biology) Maladaptation to changing conditions could lead to extinction
Environmental change
Extinction threshold
Maladaptation Extinction
(Hamilton and Miller 2016, Conservation Biology) Evolutionary rescue from standing genetic variation
Environmental change
Rescue via standing variation
Extinction threshold
Maladaptation Extinction
(Hamilton and Miller 2016, Conservation Biology) Gene flow reduces demographic consequences of maladaptation
Environmental change
Introduction Rescue via gene flow * of variation
Rescue via standing variation
Extinction threshold
Maladaptation Extinction
(Hamilton and Miller 2016, Conservation Biology) One of the rarest pine species in the world, Torrey pine is restricted to one mainland and one island population Santa Rosa Island an expanding population Torrey Pines State Reserve abiotic and biotic challenges Genetics: exceptionally low levels of genetic diversity in a conifer • 59 allozyme gene loci surveyed by Ledig and Conkle (1983) • Chloroplast gene sequences revealed only a few between population variable sites (Whittall et al. 2010) Genetic uniformity may leave trees vulnerable to pests, pathogens and environmental change(Whittall et al. 2010) (Ledig and Conkle 1983) Common garden experiment: Permit evaluation of fitness variation within and among Mainland, Island and F1 individuals in a common environment Mainland Population (San Diego) Island Population (Santa Rosa Island – Channel Islands) F1 (♂ Mainland x ♀ Island)
Is Torrey pine a candidate for genetic rescue? Is there variation within populations? Are hybrids more ‘fit’? and what does this mean to conserving evolutionary potential? Distinct growth trajectories across time Will the mainland population ‘catch up’ to the hybrids?
400 Mainland F1 Hybrid
300 Island
) Type
m
(
M
t
h
g h i 200
e
H i
Height (m) Height 100
0
2008 2010 2012 2014 2016 2008 2010 2012Year 2014 2016 Year (Hamilton et al. 2017, Ecology & Evolution) How has reproductive output changed over time?
Increase in the mean frequency of conelets produced per maternal tree over time in hybrid and mainland trees 2013 2014 2015
Mainland e 0.4
v i 0.75
t
c
u 0.4
f
d F1 Hybrid
o
o 0.3
r
n
p
o
i
e
t 0.50
r
r Island
o
s
l
p 0.2
a
o
u r 0.2
d
P
i
v
i 0.25 Reproductive d 0.1
n
i
0.0 0.0 0.00 Proportion of Individuals Proportion 1 11 14 17 4 6 7 8 M 1 11 14 17 4 6 7 8 M 1 11 14 17 4 6 7 8 M Parent Parent Parent Gap in knowledge: the consequences of genetic rescue in the short and long-term? • Is fitness observed in F1s maintained in advanced generation Torrey pine (F2s and beyond)? Opportunity: compare fitness across parent, F1, F2, BC-X progeny in a 2nd generation common garden
• Is there inbreeding in native populations of Torrey pine? Opportunity: use genomic data to evaluate inbreeding and regions of the genome exhibiting excess homozygosity
• Have barriers to reproduction evolved between populations? Opportunity: common garden and crossing experiments to evaluate environmental and non-environmental barriers Key to conservation of rare species: building collaborative partnerships
Thank you to all individuals across institutions that continue to make this research possible