The bristle millipedes (Diplopoda, Penicillata, Polyxenida) of the Iberian Peninsula, Balearic and Canary Islands with new records and data on their distribution

Abstract

Polyxenida, commonly known as bristly or pincushion millipedes, is a small order of millipedes, usually found in dead wood, under bark on dead logs and living trees and scrubs, in soil, leaf litter and under rocks. Given their small size and elusive nature, they have been frequently overlooked, and available information of most species is very limited. Their distribution and diversity in most regions of the Iberian Peninsula, the Balearic Islands and the Canary Islands are still largely unknown. Here we compile both published and new records for Polyxenida species in these three geographical areas. We also present pictures of living specimens of several species. In the studied regions there are representatives of three families, 5 genera and at least 10 species. In the family Synxenidae, only one species, Phryssonotus platycephalus (Lucas, 1846), occurs on in the Iberian Peninsula and the Balearic Islands. The Polyxenidae is more diverse: Polyxenus lagurus (Linnaeus, 1758) is widespread in the Iberian Peninsula and the Balearic Islands, where there could be yet another species of Polyxenus Latreille, 1804; in the Canary Islands there is a possibly introduced widespread species, P. fasciculatus Say, 1821, and one endemic, P. oromii Nguyen Duy-Jacquemin, 1996; the genus Macroxenus Brolemann, 1917 is represented by M. rubromarginatus (Lucas, 1846) in the Iberian Peninsula and M. enghoffi Nguyen Duy-Jacquemin, 1996, probably another endemic species, in the Canary Islands. Finally, in the family Lophoproctidae we find Lophoproctus jeanneli (Brolemann, 1910) both on the Iberian Peninsula and the Balearic Islands; L. lucidus (Chalande, 1888), reported here for the first time from the Iberian Peninsula and El Hierro Island; L. pagesi Condè, 1981, endemic to caves in Mallorca, with a closely related form, L. cf. pagesi also from caves in Portugal; Lophoproctinus inferus inferus (Silvestri, 1903), with a few records from Mallorca, and L. i. maurus Marquet & Condè, 1950, known from the Canary Islands. Our new records, as well as those from the citizen science initiative iNaturalist, notably expand the known distribution ranges of several Polyxenida species in the Iberian Peninsula. Many species show very fragmented distribution patterns, with isolated records in different geographical areas. Further study including more intensive sampling and molecular data will help to understand the true nature of such patterns.