Abstract
Many pygmy grasshopper species exhibit colour-marking polymorphism. However, this polymorphism in some species, such as Tetrix bolivari, is almost unknown. The aim of this work is to identify using DNA barcoding the colour-marking polymorphic morphs of this pygmy grasshopper species collected from both grass and sand microhabitats. Analysis by NJ clustering and pairwise distances indicated that all specimens collected showing colour-marking polymorphism are species of Tetrix bolivari. Haplotype network construction showed ten different haplotypes from a total of 57 Tetrix bolivari individuals with H1(82.5%) being the most common type and it also displayed low divergence within Tetrix bolivari population. The haplotype analyses were consistent with the NJ clustering. Our field census showed the frequency of Tetrix bolivari morphs differed significantly, with the rank order of morphs (from high to low) typeA1, type B1, type A2, type A3, type A4, type A5, type A6, type A7, type B2, type B3, and type B4. The most common type A morphs were without contrasting markings, while the rarer type B morphs have contrasting white markings. We suggest that type B morphs have greater camouflage effects against natural backgrounds such as grass or sand than type A morphs. Both our field census and haplotype analysis revealed that type A has higher frequency and more haplotypes than type B.
Highlights
Pygmy grasshoppers are typical examples of polymorphic species (Holst 1986, Ichikawa et al 2006)
Our NJ analysis showed that the 56 individuals with different colour-marking morphs clustered with T. bolivari into one clade with bootstrap value of 100% (Fig. 1)
According to the above analysis, we inferred that all pygmy grasshoppers with different morph types in this research are all species of T. bolivari
Summary
Pygmy grasshoppers are typical examples of polymorphic species (Holst 1986, Ichikawa et al 2006). Some species are highly polymorphic in colour and markings even within a single population (Forsman 2000). Such polymorphism has adaptive significance which can provide camouflage for the species against their natural backgrounds (crypsis), such as grass or sand (Ruxton et al 2004, Stevens and Merilaita 2009, Cott 1940, Thayer 1909). For certain morphs with contrasting marking, such as longitudinal morphs of Tetrix japonica, they tended to be more common in the sand microhabitat where they were more conspicuous compared to the grass background where the markings provided a stronger camouflage effect for them.
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