DOI: 10.5061/dryad.wh70rxwk8
title: Climate and ice in the last glacial maximum explain patterns of isolation by distance inferred for alpine grasshoppers

description: Aim: Cold-adapted species are likely to have had widespread ranges with
 greater connectivity of populations during the last glacial cycle. We
 sought evidence of this in the level and distribution of variation within
 one alpine insect species. Location: Southern Alps, New Zealand Taxon: The
 endemic, wingless, alpine grasshopper Sigaus australis (Orthoptera:
 Acrididae) Methods: The current fragmented alpine distribution of Sigaus
 australis was used to estimate its environmental envelope (niche) and this
 model was then used to infer the extent of available habitat for the
 species during the last glacial maximum. We subtracted the area covered by
 ice to infer available habitat and compared fragment size. Using our
 prediction of a more continuous species range we sought evidence of past
 gene flow in the form of isolation by distance using phenotypic and
 genetic variation. We used geometric morphometrics of pronotum shape and
 DNA sequencing (mitochondrial ND2) to document variation. Results: The
 current distribution of Sigaus australis is of a similar size to that
 inferred during the last glacial maximum when valley glaciers would have
 covered much of the climatically suitable land. However, the current
 distribution of S. australis is more fragmented than inferred from the
 past distribution of suitable habitat. Clinal patterns of pronotum shape
 variation and signatures of isolation by distance support the hypothesis
 of a formerly more connected species. A north/south division was observed
 in pronotum shape but this phenotypic difference was not diagnostic, as
 one would expect within a single species.   Main conclusions: The
 distribution of ice during the last glacial maximum significantly alters
 inferred habitat availability revealing that models of past and future
 habitat need to include more than just climate variables to provide
 reliable inferences. Flightless alpine species that are currently
 restricted to fragmented high elevation locations are likely to harbour
 high levels of genetic diversity.
description: We collected Sigaus australis grasshoppers from 27 locations in
 South Island New Zealand, extending the documented range of this species.
 Location records were acquired for 14 species of New Zealand endemic
 grasshoppers were compiled with data from our own grasshopper collections
 to produce a binary table where the presence or absence of S. australis
 was recorded for each location. Analysis of shape variation used fourteen
 landmarks identified around the perimeter and the dorsal surface of the
 pronotum on each image of 503 grasshoppers. Landmarks 1, 2, 6, 8 and 12
 relate to the main angles of the pronotum dorsal perimeter, 13 and 14 are
 at the intersection of sulci (surface grooves) with the dorsal midline, 3,
 4, 5, 9, 10 and 11 on the lateral carinae. X and Y coordinates are then
 assigned to each landmark. Polymerase chain reaction designed to target
 the mitochondrial DNA gene NADH dehydrogenase 2 was used to produce the
 alignment data.
description: David Carmelet*, Mary Morgan-Richards<sup>1</sup>,
 Emily M. Koot<sup>2</sup>, Steven A.
 Trewick<sup>3</sup><br>
 *,<sup>1</sup>,<sup>3</sup> Wildlife and Ecology,
 School of Agriculture & Environment, Massey University, Private
 Bag 11-222, Palmerston North, New Zealand.<sup>2</sup> New
 Zealand Institute for Plant and Food Research Ltd: Palmerston
 North, Manawatu, NZ*dcarmelet@gmail.com* https://orcid.org/0000-0002-9524-7588<sup>1</sup> https://orcid.org/0000-0002-3913-9814<sup>2</sup> https://orcid.org/0000-0002-1956-3415 <sup>3 </sup>https://orcid.org/0000-0002-4680-8457   GeneticSAtable.csv : Distribution of specimen used for the population genetic analysis Presence.Data.csv : Presence/absence data used for the niche modelling MorphometricSAtable.csv : Distribution of specimen used for the geometric morphometrics analysis LandmarkData.TPS : Coordinates and scale of the landmarks used for the geometric morphometrics analysis AlignmentSA.fasta : The fasta file of the alignment of ND2 partial gene used for the population genetic analysis