Mitrapsylla rupestris sp. nov., a psyllid (Hemiptera, Psylloidea) associated with Poiretia bahiana (Fabaceae) endemic to the Espinhaço mountain range (Brazil, Bahía)

Mitrapsylla rupestris sp. nov., associated with Poiretia bahiana C. Mueller (Fabaceae, Faboideae, Dalbergieae), is described, diagnosed and illustrated. The new species is morphologically similar to M. aeschynomenis, M. aurantia, M. cubana and M. didyma from which it differs in details of the terminalia and the host plant. Poiretia constitutes a previously unknown psyllid host. As its host, Mitrapsylla rupestris sp. nov. is probably endemic to rock habitats of the Espinhaço Range in eastern Brazil. These rock habitats display a high species diversity but are seriously threatened by human activities. More research on these habitats is urgently needed to design efficient conservation strategies.


Introduction
The Serra do Espinhaço, a mountain range in eastern Brazil (states of Bahía and Minas Gerais), is famous for its high floristic diversity and endemism. Both, species richness and narrow endemism, are mostly concentrated in the "campos rupestres" (= rock fields, rupestrian fields) (Rapini et al. 2008). The disjunct distribution of the rock fields along the Espinhaço Range with extreme environmental conditions and the heterogeneity of habitats are responsible for this huge plant diversity (Ribeiro et al. 2014). The Espinhaço Range harbours around 10% of the angiosperm species known from Brazil even though it covers less than 1.5% of the Brazilian territory (Ribeiro et al. 2014), and up to a third of its plant species are endemic (Giulietti et al. 1987;Carneiro et al. 2009). Examples of taxa that are concentrated in rock fields have been reported from the Apocynaceae, Eriocaulaceae, Melastomataceae and Orchidaceae (Ribeiro et al. 2014).
Much less is known about host specific, phytophagous insects from the Espinhaço Range. The study of Carneiro et al. (2009), showing that in this mountain range, rock fields bear the highest species richness of gall-inducing insects, suggests that the entomofauna of the Espinhaço Range may be similarly diverse and rich in endemics as the flora.
Psylloidea or jumping plant lice are highly host specific phloem-feeders. The world fauna comprises just over 4000 described species but the fauna of the tropics is generally poorly known, and many more species can be expected. From Brazil 160 species have been reported (Burckhardt and Queiroz 2021) but there may be as many as 1000 species (Burckhardt and Queiroz 2012). A recent survey of the psyllid fauna of the Serra do Espinhaço produced many undescribed species, among them also five species from "campos rupestres". Here we describe one of them, Mitrapsylla rupestris sp. nov., associated with Poiretia bahiana C. Mueller (Fabaceae, Faboideae, Dalbergieae), a species that is endemic to rocky habitats in the Espinhaço Range (Müller 1986). Mitrapsylla constitutes a neotropical genus of around 50 described species whose Brazilian members were recently revised (Rendón-Mera et al. 2020).

Material and methods
Material is deposited in the Naturhistorisches Museum, Basel, Switzerland (NHMB) and the Coleção Entomológica Padre Jesus Santiago Moure, Centro Politécnico, Universidade Federal do Paraná, Curitiba, PR, Brazil (UFPR). The morphological terminology follows mostly Halbert and Burckhardt (2020) and Rendón-Mera et al. (2020). Measurements were taken as follows: adult body length from specimens preserved in 70% ethanol, measuring the distance between fore margin of head and tip of forewings when folded over body; the other measurements were taken from slide-mounted specimens. The measurements and ratios are given as range. For the identification of specimens, we used the key of Rendón-Mera et al. (2020) and the psyllid collection of the NHMB. The nomenclature and classification of Psylloidea follows Burckhardt and Queiroz (2021), that of the plants accords with the World Flora Online (2021).

Mitrapsylla Crawford
Notes. With currently 51 described species, the neotropical Mitrapsylla constitutes the largest genus of Ciriacreminae (Psyllidae). It occurs from the southern United States in the north to northern Argentina in the south with 40 species reported from Brazil. The genus was reviewed by Rendón-Mera et al. (2020) who provided descriptions of the genus and the Brazilian species, an identification key to males of the Brazilian species and a list of host plants. These belong to the subfamilies Caesalpinioideae, Detarioideae and Faboideae (Fabaceae). The genus is morphologically homogeneous and differences between species are often small. Paratypes. Brazil, 5 males, 6 females, Bahía, same data as holotype (NHMB, UFPR, dry, slide, ethanol 70%, NMB-PSYLL0007048-NMB-PSYLL0007055).
Diagnosis. Adult head and thorax with pattern consisting of fine whitish lines and dots. Genal processes irregularly conical, subacute apically, 0.5-0.7 times as long as vertex along midline. Forewing with surface spinules usually present in all cells but much reduced, present in cell c+sc at the apex, in r 1 along apical margin, in r 2 in apical half of cell, in m 1 in apical third or half, in m 2 in basal half and near apex of cell, in cu 1 almost completely reduced, in cell cu 2 covering most of the cell but leaving broad spinule-free stripes along the veins; radular spinules present in cells m 1 , m 2 , cu 1 and sometimes in r 2 . Paramere, in profile, narrow, clavate; sclerotised ridge apically, more or less in the middle, in dorsal view bearing two small teeth. Distal segment of aedeagus complex, with unipartite dorsal lobe. Female proctiger, in profile, with dorsal outline weakly indented adjacent to circumanal ring, in apical half almost straight or weakly convex; apex narrowly rounded.
Description. Adult (Figs 4-7). Colouration. Orange to brown. Head and thorax with pattern consisting of fine whitish lines and dots (Figs 5,7,8). Ocelli orange, eyes grey. Antennal segments 3-7 yellow at base, dark brown at apex, dark portion becoming longer from proximal to distal segment; segments 7-10 dark brown. Head, clypeus and thorax yellow in ventral view. Thoracic pleura irregularly brown with dark margins of sclerites (Figs 4,6). Legs yellow or brown, tarsi greyish brown. Forewing (Figs 10, 12) transparent, colourless or slightly yellowish with small dark brown dots on radular spinules in cells m 1 , m 2 and cu 1 as well as at apex of clavus; veins light brown with brown tips. Hindwing whitish, transparent. Abdominal sclerites brown with two longitudinal submedian rows of whitish dots on tergites; intersegmental membranes yellow or orange. Apex of paramere and female terminalia black. Young specimens lighter with less expanded dark colour, getting gradually darker with age.
Fifth instar immature unknown, only first and second instars available.
Etymology. From Latin rupes = rock, referring to its occurrence in rock habitats; rupestris is an adjective in the nominative case, feminine.
Distribution. Brazil (Bahía) where it is probably endemic to the Serra do Espinhaço.
Comments. Mitrapsylla rupestris sp. nov. resembles M. aeschynomenis Rendón-Mera, Burckhardt, Cavichioli & Queiroz, 2020, M. aurantia Rendón-Mera, Burckhardt, Cavichioli & Queiroz, 2020, M. cubana Crawford, 1914, and M. didyma Rendón-Mera, Burckhardt, Cavichioli & Queiroz, 2020, in the apically weakly expanded paramere, in profile, bearing the sclerotised apical ridge medially and in the unipartite dorsal lobe on the distal portion of the aedeagus. Mitrapsylla rupestris sp. nov. differs from the four species in the lateral tubercles on the ventral aedeagal process which are situated near the apex (rather than near the middle), and in the female proctiger which is dorsally straight or weakly convex in apical half (rather than weakly sinuous) and narrowly rounded apically (rather than obliquely truncate). In M. aeschynomenis and M. aurantia, the antennae and the genal processes are slightly shorter: antenna length/ head width ratio < 2.1 versus > 2.1 in M. rupestris sp. nov.; length ratio of genal processes/ vertex < 0.5 versus > 0.5 in M. rupestris sp. nov. From the former, M. rupestris sp. nov. differs also in the slightly more acute genal process-es and from the latter in the more spaced surface spinules of the forewing. In the key of Rendón-Mera et al. (2020), M. rupestris sp. nov. runs to couplet 31 together with M. cubana and M. didyma from which is differs the shape of the sclerotised ridge of the paramere in dorsal view. In the last two species, the ridge bears one big posterior tooth, while in M. rupestris sp. nov. it forms two small teeth. From the former it differs in the apically slightly more expanded paramere and from the latter in the slightly shorter postero-apical lobe of the paramere. It differs also in the host association: M. aeschynomenis develops on Aeschynomene, which belongs to the same tribe as Poiretia (Dalbergieae), M. cubana and M. didyma are associated with Desmodium, which is a member of the more distantly related Desmodieae within the same subfamily (Faboideae). The host of M. aurantia is unknown.

Discussion and conclusions
Hosts are known for 34 of the 51 previously known Mitrapsylla species (Rendón-Mera et al. 2020 Sophoreae: Sophora). Poiretia bahiana (tribe Dalbergieae), the host of M. rupestris sp. nov., constitutes a previously unknown psyllid host. All Mitrapsylla species for which hosts are known are either monophagous on a single host species or oligophagous on several species of the same host genus. In terms of host taxon and range, M. rupestris sp. nov. fits the general pattern of Mitrapsylla.
True endemism in psyllids is probably rare and apparently restricted distributions may merely reflect incomplete faunistic knowledge. Among the 40 Mitrapsylla species previously reported from Brazil, 26 have a relatively wide geographic distribution and are also known from outside of Brazil or have been recorded from two or more states in Brazil (Rendón-Mera et al. 2020). Of the remaining 14 species, 10 are known from only a single municipality. Whether these species are endemic or just reflect insufficient sampling cannot be judged without more fieldwork. For three of the 10 species the hosts are known: M. aeschynomenis (on Aeschynomene paniculata), M. hamata Rendón-Mera, Burckhardt, Cavichioli & Queiroz, 2020 (on Machaerium amplum) and M. pterogynis Rendón-Mera, Burckhardt, Cavichioli & Queiroz, 2020 (on Pterogyne nitens). All three hosts are widely distributed suggesting that the associated psyllids also may be. Mitrapsylla rupestris sp. nov., in contrast, is probably narrowly endemic as it is monophagous on Poiretia bahiana, an endemic of rock habitats of the Serra do Espinhaço (Müller 1986).
The flora of the "campos rupestres" of the Espinhaço Range is extremely species rich with a high degree of endemism (Ribeiro et al. 2014). The psyllids seem to reflect this pattern. Apart from Mitrapsylla rupestris sp. nov., we found in these rock fields also two Isogonoceraia spp. (Psyllidae, Ciriacreminae) on Chamaecrista (Fabaceae), one Heteropsylla sp. (Psyllidae, Ciriacreminae) on Calliandra (Fabaceae) and one Trioza sp. (Triozidae) on Eugenia (Myrtaceae). The four species are undescribed, probably host specific and endemic to "campos rupestres" of the Serra do Espinhaço. Despite their floristic and faunistic interest, there is a lack of studies of the mountainous regions of Brazil, which harbour some of the most threatened plant ecosystems (Bünger et al. 2014). Studies on the flora and fauna are urgently required for designing efficient measures for the sustainable conservation of this unique biome.