Lack of assortative mating might explain reduced phenotypic differentiation where two grasshopper species meet
Data files
May 06, 2024 version files 252.07 KB
Abstract
Hybridization is an evolutionary process with wide-ranging potential outcomes, from providing populations with important genetic variation for adaptation to being a substantial fitness cost leading to extinction. Here, we focussed on putative hybridization between two morphologically distinct species of New Zealand grasshopper. We collected Phaulacridium marginale and Phaulacridium otagoense specimens from a region where mitochondrial introgression had been detected and where their habitat had been modified by introduced mammals eating the natural vegetation and by the colonization of many non-native plant species. In contrast to observations in the 1970s, our sampling of wild pairs of grasshoppers in copula provided no evidence of assortative mating with respect to species. Geometric morphometrics on the pronotum shape of individuals from areas of sympatry detected phenotypically intermediate specimens (putative hybrids), and the distribution of phenotypes in most areas of sympatry was found to be unimodal. These results suggest that hybridization associated with anthropogenic habitat changes has led to these closely related species forming a hybrid swarm, with random mating. Without evidence of hybrid disadvantage, we suggest a novel hybrid lineage might eventually result from the merging of these two species.
README: Lack of assortative mating might explain reduced phenotypic differentiation where two grasshopper species meet
Authors: Mary Morgan-Richards, Maurine Vilcot, Steven A. Trewick
The data are mitochondrial DNA sequences and morphometric values relating to variance among Phaulacridium (Insect, Orthoptera, Acrididae) grasshoppers that were sampled in Aotearoa (New Zealand).
The morphometric data are 'traditional' metrics of eight nonindependent variables comprising three size differences (hind femur length, hind tibia length, and tegmina length), three ratios and two angles of the pronotum margin in dorsal view; and geometric coordinates derived from twelve geometric landmarks were identified and digitized around the perimeter of the dorsal surface of the pronotum.
DNA sequences result from Sanger sequencing of PCR products from 95 individual grasshoppers. With previous data, this provides an alignment of nucleotide data for 243 individuals.
Description of the data folder:
Folder: Data
This folder contains four files including:
- Phaulacridium COI.phy: Fasta file containing Mitochondrial DNA cytochrome oxidase subunit 1 sequence data, 755bp long.
- PC_eigenvalues.csv
- PC_scores.txt
- Phaulacridium_measurements.csv: individual information and morphometrics measurements
Variables in Phaulacridium_measurements.csv:
- Code, Individuals: individual identifiers
- Lname, LocationName, L: short name, long name and number associated to the sampling location
- Sex: sex of the individual
- In copula: whether the individual was caught in pair or alone
- Pair_code: if caught in pair, the identifier of the pair
- Latitude, Longitude: sampling coordinates
- Year, Date: sampling date
- PA1: pronotum angle 1 as the lateral carinae pronotum angle with vertical sulcus (°)
- PA2: pronotum angle 2 as the Lateral carinae pronotum angle with first transverse sulcus (°)
- PW1: pronotum width (mm)
- PW2: pronotum width at the narrowest point (mm)
- PW3: pronotum width at the widest point (mm)
- PL: pronotum length (mm)
- TeL: tegmina length (mm)
- FL: femur length (mm)
- FW: femur width across the third muscle band (mm)
- TL: tibia length(mm)
- HL: head length (mm)
- HW: head width (mm)
- HW/HL, FL/FW, PW1/PW2, PW3/PL: ratios of the above variables
Folder: Output
This folder contains 4 CSV files that are direct outputs from the scripts detailed below.
Variables not defined above:
- cluster_trad: cluster info based on traditional morphometrics
- uncertainty_trad: uncertain species identification based on traditional morphometrics
- Species_traditional: species identification based on traditional morphometrics
- Female: female assignment
- Uncertainty_Female: uncertain female assignment
- Male: male assignment
- Uncertainty_Male: uncertain male assignment
- Pair_type: in copula male and female species combination (marginale/marginale, marginale/otagoense, otagoense/otagoense)
- d'Agostino Omnibus: d’Agostino omnibus normality test
- DB: Bannockburn Sluicings sample location
- DQ: Quartz Reef sample location
- HR: Hawkesdun Road sample location = DH
- AW: Awaroa sample location
- AG: Graveyard Gully sample location = AxG
- AL: Little Valley Road sample location = AxL
- AM: Asample location
- TE: Tekapo east sample location = TeE
- TW: Tekapo west sample location = TeW
- Code: unique sample code for each specimen
- V1-V4: assignment probabilities to each of the 4 clusters from Gaussian mixture model assignment based on pronotum geometric landmark data (V1 P. marginale female, V2 P. otagoense male, V3 P. otagoense female, V4 P. marginale male)
- Species_geometric: species identification based on geometric data
- cluster_pronotumPC2: assignment from second principal component of pronotum shape variation
- Sex_geometric: sex identification based on geometric data
- marginale_membership: assignment score to marginale taxon group
- otagoense_membership: assignment score to otagoense taxon group
Sharing/Access information:
The data are also available publicly at the research group website (link in Related Works section).
Part of the data and their derivation were previously reported in the following Insect Conserv Divers article, which includes details of PCR and sequencing of DNA, and 'traditional' morphometric data collection:
Sivyer, L., Morgan-Richards, M., Koot, E. and Trewick, S.A. (2018), Anthropogenic cause of range shifts and gene flow between two grasshopper species revealed by environmental modelling, geometric morphometrics and population genetics. Insect Conserv Divers, 11: 415-434.
Code/software:
Procrustes analysis, PCA, and ANOVA from pronotum landmarks were made on MORPHOJ. All other analysis were performed in R, and are reproducible with this folder. Detailed annotations and the library used are provided throughout the scripts.
- 01_Traditional_morphometrics.R: This R script reproduces the clustering and species identification from the measurement data
- 02_Geometric_morphometrics.R: This R script reproduces the clustering analysis, normality test and from pronotum landmarks