Immigration delays but does not prevent adaptation following environmental change: experimental evidence
Data files
Mar 19, 2024 version files 631.02 KB
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all_blocks-rescue-1-7-update-apr23.csv
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Deltamethrin_Dosage_BIG.csv
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JEB_Durkee-et-al-2024.Rmd
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maternal_effects_gen.csv
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order-experiment-gen1.csv
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pop_numbers.csv
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README.md
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reciprocal-transplant-update-apr23.csv
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rescue-apr23.csv
Abstract
In today’s rapidly changing world, it is critical to examine how animal populations will respond to severe environmental change. Following events such as pollution or deforestation that cause populations to decline, extinction will occur unless populations can adapt in response to natural selection, a process called evolutionary rescue. Theory predicts that immigration can delay extinction and provide novel genetic material that can prevent inbreeding depression and facilitate adaptation. However, when potential source populations have not experienced the new environment before (i.e., are naive), immigration can counteract selection and constrain adaptation. This study evaluated the effects of immigration of naive individuals on evolutionary rescue using the red flour beetle, Tribolium castaneum, as a model system. Small populations were exposed to a challenging environment, and three immigration rates (zero, one, or five migrants per generation) were implemented with migrants from a benign environment. Following an initial decline in population size across all treatments, populations receiving no immigration gained a higher growth rate one generation earlier than those with immigration, illustrating the constraining effects of immigration on adaptation. After seven generations, a reciprocal transplant experiment found evidence for adaptation regardless of immigration rate. Thus, while the immigration of naive individuals briefly delayed adaptation, it did not increase extinction risk or prevent adaptation following environmental change.
README: Immigration delays but does not prevent adaptation following environmental change: experimental evidence
Corresponding authors: Lily F. Durkee, l.durkee@colostate.edu; Ruth A. Hufbauer, ruth.hufbauer@colostate.edu
Data collected and code written by: L. F. Durkee
Raw data file descriptions
Among all files, "NA" is used to represent null values.
1) all_blocks-rescue-1-7-update-apr23.csv
Description: census data from the rescue experiment for every generation (gen
)
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gen
: whole numbers represent numerical generations;gen
of 1.01, 2.01, etc. represents the timing of the immigration event (1 or 5 migrants each gen) -
block
: temporal block, 3 total (A, B, and C) -
array
: the set of populations using the same source population, labeled 1-8 in blocks A & B, 1-9 in block C (25 total) -
unique_array
: unique array name for every array -
group_rt
,boxID_rt
: different group numbers for populations included in the reciprocal transplant experiment; ID used during the reciprocal transplant experiment -
type
: "sink" refers to experimental populations exposed to the challenging environment; "source" refers to source populations. -
trt
: 0, 1, or 5 migrants every generation (0/gen, 1/gen, 5/gen, respectively); all "1 event" patches were removed from the experiment -
MO
: "migrant origin" refers to the dispersal array - dispersing migrants are indicated by "box 4" and 0-migrant populations are indicated by "none". All populations receiving "box 1" migrants were removed from the experiment. -
init_N
: the number of parents that started the generation -
census_N
: the number of adults produced after 35 days -
mig_N
: the number of migrants added -
new_N
: the population size after immigration -
pupae
,larvae
,dead
: the number of pupae, larvae, and dead adults counted during census; not included in the analysis -
trt_key_new
,trt_order_new
,trt_key_old
,trt_order_old
,trt_key_new1
,boxID
: Combinations of variables used to create a unique ID for each population (boxID
) -
changed_to_ctrl
,changed_to_control
: both used to indicate if "1 event" patches were changed to 0-migrant populations after receiving no migrants throughout the experiment; these were removed from the analysis -
extinct
,pathogen
: 1/0 indicators if the populations went extinct or naturally went extinct due to pathogen infection
2) rescue-apr23.csv
Description: Census data formatted for the growth rate analysis; variable names are the same as above, with a few additional ones described below.
rescue3
,rescue2
,rescue1
: three definitions of rescue-
rescue3
: previous three generations had growth rate > 1 -
rescue2
: previous two generations had growth rate > 1 -
rescue1
: the complement of extinct
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lambda
: growth rate for that generation, calculated ascensus_N
(t) /init_N
(t-1)
3) reciprocal-transplant-update-apr23.csv
Description: data from the reciprocal transplant experiment (gen 9). Several of the variables are repeated from the two described datasets. New variables are described below.
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pop_num
: new unique ID given to each population during the reciprocal transplant experiment -
patch_type
: same astype
above -
rescue_trt
: the immigration rate used throughout the rescue experiment; "total" refers to source populations -
treatment
: "migration" (1 or 5 migrants), "no migration" (0 migrants), or "source" -
init_date
,census_date
: the date the populations were initiated and censused, respectively -
double
: refers to whether a "double set up" (populations initiated over 2 days with the same parents, done only for small populations) was used during the common environment generation -
environment
: the concentration of deltamethrin used in the reciprocal transplant experiment -
init_N
: 40 parents initiated every population this generation;init_N
< 40 were removed from the analysis -
census_N
: the number of adults produced after 35 days -
pup
,lar
: pupae and larvae produced after 35 days (not included in the analysis)
4) maternal_effects_gen.csv
Description: data from the common environment generation (gen 8)
-
age
: age of parents; numbers of 34 and 35 for the same pop_num indicate a double setup was performed -
treatment
: immigration rate used during rescue experiment -
treatment
: population treatment during the rescue experiment (0, 1, or 5 migrants, 1 event [removed from analysis], or source) -
rep
: replicate number
5) pop_numbers.csv
Description: the unique population numbers for every replicate; in the script, this file is merged with the above files to assign unique integers (pop_num
) to every population. Repeated variable names are defined above.
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pop_num
: unique integer assigned to every experimental and source population -
trt_key
: the combination oftype
,trt
, andMO
(all defined above) -
boxID
: unique code assigned to each population
6) Deltamethrin_Dosage_BIG.csv
Description: Data from the preliminary experiment used to determine the dose of deltamethrin to use during the rescue experiment
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Strain
: "All Red Mix" refers to the original stock population of beetles used to initiate this experiment -
ppm
: refers to concentration in ppm in the test environment -
Box
: replicate number for each patch -
Init_N
: 50 parents were used to initiate each population -
Census_N
: the number of adults produced by day 35 -
Age
: refers to the age of the parents; "old" refers to 35-day-old parents, "young" refers to 28-day-old parents
7) order-experiment-gen1.csv
Description: Data from the order experiment, which tested whether the order of set-up affected growth rate. We present the results from the first generation. The protocol for this experiment closely mimicked the rescue experiment, except the treatments were simply the order of the patches (1-7). After this experiment, we removed the first three patches (the populations receiving "box 1" migrants) due to significant differences in growth rate due to the order of setup. We saw no difference in growth rate for patches 4-7, the treatments included in the final analysis.
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Array
: unique integers for each population grouping of 7 patches (to mimic the rescue experiment) -
Trt
: the order of the patch in the array, ranges from 1-7