Rapid turnover of a pea aphid superclone mediated by thermal endurance in central Chile

Global change drivers are imposing novel conditions on Earth's ecosystems at an unprecedented rate. Among them, biological invasions and climate change are of critical concern. It is generally thought that strictly asexual populations will be more susceptible to rapid environmental alterations due to their lack of genetic variability and, thus, of adaptive responses. In this study, we evaluated the persistence of a widely distributed asexual lineage of the alfalfa race of the pea aphid, Acyrthosiphon pisum, along a latitudinal transect of approximately 600 Km in central Chile after facing environmental change for a decade. Based on microsatellite markers, we found an almost total replacement of the original aphid superclone by a new variant. Considering the unprecedented warming that this region has experienced in recent years, we experimentally evaluated the reproductive performance of these two A. pisum lineages at different thermal regimes. The new variant exhibits higher rates of po..., Sampling and laboratory rearing
In a previous study [47], A. pisum individuals were sampled from alfalfa fields in the spring and summer of 2017-2018 in central Chile, the same region previously surveyed by Peccoud et al. [23] in 2006-2007 (latitude 35 to 40 ºS, see [47]). This study showed that there were only two MLGs in this area (named APG2 and APG3 in [47]), with 96% of the genotyped individuals belonging to APG3 and the remaining 4% to APG2. Clonal lineages were established in the laboratory from these two MLG by rearing them separately on broad bean plants (Vicia faba L.) inside 4 L transparent plastic buckets, kept in a climatic chamber at 20°C (± 0.5°C) with a long photoperiod (LD = 16:8) to ensure their sustained parthenogenetic reproduction [46, 50]. Five aphids from each lineage were taken before performing the experimental procedures on the thermal response (see below), and their DNA was extracted to confirm their genetic profile.
Genetic profiles and secondary symbionts as..., Data analysis
Since the MLGs used in this study came from the same region previously surveyed by Peccoud et al. [23], a Neighbor-Joining (NJ) tree of MLGs was built with the MLGs found in this study and those found by Peccoud et al. [23] using the seven original microsatellite markers to make both studies comparable. NJ tree was constructed based on a distance matrix of allele shared distances (DAS) with bootstrapping of 1000 replicates and computed by the software Populations v1.2.31 [57].
To analyze and compare the intrinsic growth rate of each lineage within their thermal niche, we fitted a linear model after a visual diagnostic of the data using constant acclimation temperature and MLG as independent variables and intrinsic growth rate as dependent variable. Then, predicted values of rm were used to show how detected differences in rm between genotypes could be translated into an ecologically relevant scenario. We assessed how daily population growth and cumulative population size a..., Script and data for:

Martel et al. \"Rapid turnover of a pea aphid superclone mediated by thermal endurance in central Chile\" (submitted).

Contains 6 files:

(1) Martel et al_SupercloneTurnover.R - R script for statistical analysis and figures.

(2) dataset_xSM.xlsx - original experimental dataset.
Variables:
\- n.sample: Mark of the experimental individual (internal use). Some individuals are marked as NA (\"not applicable\"), since they were identified and measured in a second experimental round. However, this is not crucial for the experiment.
\- Temp.trial: Experimental temperature (15, 20, 25 constant temperature; 38, 42 heat shock)
\- Gen: Genotype of each experimental individual (APG2 or APG3).
\- Edad: Age of each experimental individual in days since birth.
\- Tiempo.gen: Time between birth of experimental individual and the birth of its first nymph, in days.
\- N.crias: Total number of alive nymphs births to the 10th day since the birth of the 1st nymph.

(3) dataset_xSM...