DOI: 10.5061/dryad.f4qrfj6wv
title: Raw allelic matrix and supplementary materials: Origin and dispersion pathways of guava in the Galapagos Islands inferred through genetics and historical records

description: Guava (Psidium guajava) is an aggressive invasive plant in the Galapagos
 Islands. Determining its provenance and genetic diversity could explain
 its adaptability and spread, and how this relates to past human
 activities. With this purpose, we analyzed 11 SSR markers in guava
 individuals from Isabela, Santa Cruz, San Cristobal and Floreana islands
 in the Galapagos, as well as from mainland Ecuador. The mainland guava
 population appeared genetically differentiated from the Galapagos
 populations, with higher genetic diversity levels found in the former. We
 consistently found that the Central Highlands region of mainland Ecuador
 is one of the most likely origins of the Galapagos populations. Moreover,
 the guavas from Isabela and Floreana show a potential genetic input from
 southern mainland Ecuador, while the population from San Cristobal would
 be linked to the coastal mainland regions. Interestingly, the proposed
 origins for the Galapagos guava coincide with the first human settlings of
 the archipelago. Through Approximate Bayesian Computation, we propose a
 model where San Cristobal was the first island to be colonized by guava
 from the mainland, then it would have spread to Floreana and finally to
 Santa Cruz; Isabela would have been seeded from Floreana. An independent
 trajectory could also have contributed in the invasion of Floreana and
 Isabela. The pathway shown in our model agrees with the human colonization
 history of the different islands in the Galapagos. Our model, in
 conjunction with the clustering patterns of the individuals (based on
 genetic distances), suggests that guava introduction history in the
 Galapagos archipelago was driven by either a single event or a series of
 introduction events in rapid succession. We thus show that genetic
 analyses supported by historical sources can be used to track the arrival
 and spread of invasive species in novel habitats and the potential role of
 human activities in such processes.
description: 376 individuals of <i>Psidium
 guajava</i> were sampled for this study; 96 from mainland Ecuador
 and 280 from the Galapagos Islands (Fig. 1). Samples were grouped into
 five populations: Mainland (96 individuals), Santa Cruz (SCZ, 80
 individuals), Isabela (ISA, 95 individuals), San Cristobal (SCY, 94
 individuals) and Floreana (FLO, 11 individuals). Due to the significantly
 larger surface area of the mainland area of study, its samples were
 further grouped into nine regions based on the three geographic regions of
 continental Ecuador (Coast, Highlands and Amazon), as well as a
 latitudinal division where the extension of the country was measured from
 the northernmost tip to the southernmost one (720km), and divided in three
 latitudinal regions: North, Center, South, each one with a vertical
 extension of 240km (Fig. 1). Therefore, the nine mainland regions obtained
 were: North Coast (NC, 8 individuals), North Highlands (NH, 13
 individuals), North Amazon (NA, 12 individuals), Central Coast (CC, 11
 individuals), Central Highlands (CH, 11 individuals), Central Amazon (CA,
 8 individuals), South Coast (SC, 10 individuals), South Highlands (SH, 13
 individuals), and South Amazon (SA, 10 individuals).  Collection sites
 were georeferenced using a Garmin E-Trex Legend HCx GPS system (Garmin
 International Inc., USA). Sampled individuals were separated by a minimum
 distance of 100m from one another in order to minimize pseudo sampling
 (Urquía et al., 2019). After confirming the taxonomic identity of samples,
 two to five young leaves were collected from each individual and either
 transported to the Molecular Biology and Microbiology Laboratory at the
 Galapagos Science Center in San Cristobal or to the Plant Biotechnology
 Laboratory at the Universidad San Francisco de Quito campus in Quito,
 Ecuador, where they were stored at -20°C.  The CTAB protocol (Saghai-Maroof et
 al., 1984) was used to isolate total genomic DNA from each individual,
 after which the concentration and quality of the DNA was measured using a
 Nanodrop 1000 Spectrophotometer (Thermo Scientific, USA).
 PCR reactions of 11 SSR regions
 were performed for all samples using species-specific primers developed by
 Risterucci et al. in 2005. For amplification, a third fluorescently marked
 universal primer was incorporated, as described by Blacket et al. (2012).
 Annealing temperatures for each primer pair were optimized, with 55 ºC
 being the ideal temperature for all loci, the only exception was 54 ºC for
 the mPgCIR25 locus. The program used was 15 min at 95ºC; 30 to 40 cycles
 of 30 sec at 94ºC, 90 sec at optimized annealing temperature, 60 sec at
 72ºC, and a final step of 5 min at 72ºC. PCR products were labeled with
 one of four fluorescent dyes: 6-FAM, VIC, PIC or NED and genotyped by
 Macrogen (Seoul, Korea) using an ABI 3130 Genetic Analyzer (ThermoFisher
 Scientific, USA). Results were analyzed with the GeneMarker software v
 2.4.0 (Softgenetics, State College, PA, USA).
description: The allelic matrix uploaded shows the genotypes of the 376 guava
 individuals studied in our research. Genotypes are shown for the 11
 analyzed SSR markers. Alleles are expressed in SSR size (bp),
 including the 15 bp. from the universal primer added
 for fluorophore genotyping. The allelic matrix format is suited for
 analyses in the <em>adegenet</em> package implemented for R; a
 slash (/) separates the two different alleles in each diploid
 individual.