Agraphydrus variabilis Sexual

Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, Zoological Journal of the Linnean Society 192 (3), pp. 958-958 : 958-

Agraphydrus variabilis Sexual 18 – This paper Helochares (s.s.) lividus Sexual 18 8 + Xy p This paper Helochares (s.s.) obscurus Sexual 18 8 + Xy This paper Helochares (s.s.) punctatus Sexual 18 8 + Xy p This paper

COMPARISON WITH THE HELOPHORIDAE

The Helophoridae are the only other family of the Hydrophiloidea with karyotypes known for a wider spectrum of species ( Angus, 1982, 1983, 1986, 1989, 1992, 1996, 2015; Angus & Díaz Pazos, 1990; Angus et al., 2005, 2016; Angus & Aouad, 2009; Angus & Toledo, 2010; Angus & Jia, 2020). The family comprises a single genus Helophorus divided into ten subgenera. There are two basic karyotype numbers, 2 n = 16 + Xy p (three subgenera, 15 karyotyped species) and 2 n = 20 + Xy p (four subgenera, 41 karyotyped species). The remaining three subgenera are unknown cytogenetically. Parthenogenesis is so far known in two species, both of which show triploidy ( Angus & Jia, 2020).

Within both karyotype groups (with 18 and 22 chromosomes), there are complexes of species which are morphologically similar and hence difficult to tell apart but can be distinguished by their chromosomes. In the subgenus Helophorus s. str., Angus (1982) showed that H. aquaticus and H. aequalis had apparent differences in chromosome lengths, the position of the centromere, the amount of heterochromatin seen after C-banding and the size of the X chromosome. Similar differences were found in other cryptic species in this subgenus ( Angus, 1989; Angus & Toledo, 2010). Interestingly, the chromosomes of H. aequalis and H. grandis are similar, which contrasts with the morphology of these species. Preliminary results of the DNA analysis (Fikáček et al., unpubl.) surprisingly reveal both latter species as sister taxa, indicating that the chromosome morphology may follow the phylogenetic relationships better than morphology in this lineage. Chromosomes are more similar among the members of the species complexes in the subgenus Rhopalohelophorus . Still, clear differences between species can be found in the position of the centromere of some chromosomes and the size of the X chromosome [ H. minutus complex ( Angus, 1986, 1988); H. flavipes complex; ( Angus, 1996)]. In all these cases, the chromosomal differences among closely related species are present and more profound than we observed in most representatives of the Hydrophilidae studied in this paper. In this aspect, the hydrophilid karyotypes can be considered as more conservative at species level than those of the Helophoridae .