Filling gaps in the diversity and biogeography of Chilean millipedes (Myriapoda: Diplopoda)

Abstract

Research on the diversity and biogeography of Chilean millipedes represents a significant gap in knowledge. To reduce this gap we conducted a study: (1) to investigate the current state of knowledge of millipede diversity, and (2) to assess the pattern and causes underlying the latitudinal diversity gradient in Chilean millipedes. In Chile, 95 native millipede species have been recorded. However, rarefaction and extrapolation curves showed that increased sampling effort will reveal more species. An asymptotic estimate of diversity predicted that millipede diversity fluctuates between 125 and 197 species. The estimate, though, was based on a limited data set. Therefore, millipede diversity is probably higher than predicted. Chilean millipedes were categorized as micro-range endemics because they all have latitudinal ranges of less than 1,000 km (with 78% of species exhibiting latitudinal ranges of only ~222 km). Millipede species richness also exhibited a bell-shaped latitudinal diversity gradient, i.e. diversity peaks in the temperate climate of central Chile and decreases towards the arid and polar climates of northern and southern Chile. A multiple regression analysis revealed that this biogeographic pattern is shaped by environmental variables related to water availability, ambient energy inputs and climatic stability. These environmental variables are proxies for two of the five biogeographic hypotheses we tested in this study, i.e. the water-energy balance hypothesis and climatic stability hypothesis. Both hypotheses suggest that millipedes need stable, humid and warm climates to grow, survive and reproduce (niche conservatism). These climatic conditions are only found in central Chile, which is consistent with the diversity peak observed in that region.

Redescription of the enigmatic myriapod Hanseniella chilensis (Hansen, 1903) (Symphyla, Scutigerellidae) based on scanning electron microscope images of Chilean specimens

“…The latter scenario is plausible because Chile is surrounded by biogeographic barriers that limit species dispersal, including the Atacama Desert in the north, the Andes Mountains in the east, the Pacific Ocean in the west, and the Drake Passage to the south ( Fernández et al 2016 ). These barriers have kept Chilean biota isolated from the rest of the world for thousands of years and have favored the radiation of endemic animals, plants and microorganisms (e.g., Eisenberg and Redford Kent 1992 ; Lazo Araya 2015 ; Fernández et al 2015 , Rodriguez et al 2018 ; Campello-Nunes et al 2022 ; Parra-Gómez and Fernández 2022 ). These barriers surely represent insurmountable hurdles for animals such as symphylans.…”

Two new species of Anaulacodesmus Attems, 1898 (Polydesmida: Dalodesmidae) from temperate forest fragments in southern Chile

“…Reported body length and distribution of Anaulacodesmus (unless otherwise noted, measurements are assumed to be based on adult males). Distributions based on Schubart (1954), Parra-Gómez (2022) and Parra-Gómez & Fernández (2022) supplementary material 1 (names and occurrences of Chilean millipede species), except for the species described herein. M = male, F = female, n/a = not available, NP = National Park.…”

“…However, this is likely an under-representation of the true diversity of the group and undoubtedly numerous undescribed species remain to be discovered. Moreover, few records exist for many of the Chilean millipede taxa and the incomplete knowledge regarding their distribution, abundance, and habitat associations hinders sound management practices and effective conservation measures (Parra-Gómez and Fernández 2022).…”