Callitris, IDENTIFICATION AND ALTERNATIVE CLASSIFICATIONS

Symonds, Celia L. & Cassis, Gerasimos, 2018, Systematics And Analysis Of The Radiation Of Orthotylini Plant Bugs Associated With Callitroid Conifers In Australia: Description Of Five New Genera And 32 New Species (Heteroptera: Miridae: Orthotylinae), Bulletin of the American Museum of Natural History 2018 (422), pp. 1-229 : 12-13

CALLITRIS IDENTIFICATION AND ALTERNATIVE CLASSIFICATIONS

Callitroid-inhabiting Orthotylini are a paraphyletic assemblage found exclusively on Callitris . The most speciose and widely distributed genus of the Southern Hemisphere Cupressaceae ( Farjon, 2005) , Callitris is endemic to Australia and New Caledonia ( Hill, 1998; Pye et al., 2003), with a relictual Gondwanan distribution ( Hill and Brodribb, 1999). In addition, Callitris is allied with the monotypic New Caledonian genus Neocallitropsis ( Gadek et al., 2000) , and recent molecular phylogenetic analysis suggests that the latter genus and Actinostrobus are nested within Callitris ( Pye et al., 2003) .

In this study Callitris host plants were identified by botanists at the Western Australian (WA) Herbarium, Perth, and the Royal Botanic Gardens (RBG), Sydney. Correct identification of Callitris species can be difficult because their taxonomy is unresolved and species readily hybridize. There are two alternative classifications in contemporary use, which are variously applied in the databases of Australian state herbaria, with all names currently listed as valid scientific names, aside from Callitris tuberculata (CHAH) .

Hill (1998) recognized 17 species in his Flora of Australia treatment. Farjon (2005) in his monograph of the Cupressaceae implemented a broader species concept, recognizing 13 Callitris species. Farjon (2005) synonymized Callitris intratropica with C. glaucophylla and C. columellaris , an action not universally followed, whereas his synonymy of C. gracilis and C. tuberculata with C. preissii is widely accepted. Callitris verrucosa and C. tuberculata have been treated as either subspecies of Callitris preissii ( Harden and Thompson, 1990) or as a distinct species ( Hill, 1998).

We largely follow Hill’s treatment (1998) (see appendix 2) in our discussion and analysis of host-plant associations, and in the host-plant discussions within the species descriptions. However, host records in the type and specimens examined listings are all given as per the herbarium identifications and host-plant labels.

We do not follow the substantial nomenclatorial changes proposed by Farjon (2005), in part because the majority of identifications of our host-plant voucher specimens predate his work. In contrast, we recognize the synonymy of Actinostrobus with Callitris , based on molecular and morphological analyses ( Pye et al., 2003; Piggin and Bruhl, 2010), and the identity of species previously assigned to Actinostrobus is not confounded by their transfer to Callitris . We follow the treatment of Pye et al. (2003) in part, who recognized morphologically variable populations of Callitris at Emerald Creek Falls and Paluma (northeastern Queensland) as C. intratropica and C. endlicheri respectively.

The monophyly of Callitris columellaris , Callitris intratropica , and Callitris glaucophylla is strongly supported (Piggin and Bruhl, 2011). External characters differentiating C. columellaris , C. intratropica , and C. glaucophylla sometimes overlap, although they are readily distinguished by wood-tracheid anatomy and leaf-chemical differences (Piggin and Bruhl, 2011) and each has for the most part distinct distributions. Although molecular data was incomplete (Pye, et al., 2003), morphological analysis by Piggin and Bruhl (2011) does not support the monophyly of these three species: Callitris gracilis , Callitris tuberculata , and Callitris preissii .

For the purposes of discussion and analysis, host-plant identifications after 2005 in the Western Australian Herbarium database of Callitris columellaris were recognized as Callitris glaucophylla and records of Callitris preissii outside the Perth region were recognized as Callitris tuberculata in accordance with the above information.

Hill (1998) restricted Callitris preissii to coastal limestone plains and offshore islands in the Perth region and distinguished it from the following species that have warty fruits: C. tuberculata is more broadly distributed in Western Australia and C. verrucosa is restricted to eastern Australia. We regard the records of C. roei from South Australia as misidentifications, as this species is restricted to the Southwest Interzone phytogeographical subregion of Western Australia (records from Hill, 1998).

Identification of Callitris species is also confounded by known hybridization in the genus. For example, some of our host-plant vouchers of Callitris species could not be identified, and one specimen may represent a hybrid between C. gracilis or C. glaucophylla . Hybrid populations of these latter two species are known to occur across the mallee country and Flinders Ranges of South Australia, Victoria, and New South Wales ( Thompson and Johnson, 1986; Harden and Thompson, 1990). Callitris glaucophylla , C. gracilis , and C. verrucosa all are also known to hybridize with each other and C. glaucophylla with C. tuberculata ( Hill, 1998) .

Host-plant records and cooccurrence of callitroid orthotylines are summarized in table 3. For a list of Callitris species and synonymy, see appendix 2.

CALLITRIS FLORISTICS : Callitris species are either shrubs or trees that occur in tropical rainforest, coastal forest, and woodland, tropical savannah, semiarid to arid woodlands and shrublands, and temperate heathlands and shrublands ( Hill and Brodribb, 1999). In eastern Australia they often occur as codominant or in a mosaic pattern in mixed eucalypt forests or dense pure stands, which is in part due to changing land use and altered fire regimes ( Noble, 1997; Farjon, 2005). The majority of species occur in eastern Australia, with numerous species broadly distributed ( C. endlicheri , C. gracilis , C. rhomboidea , and C. verrucosa ). Callitris rhomboidea and C. oblonga are also found in Tasmania. Eight Callitris species occur in Western Australia with over half these species restricted to the Southwest Botanical Province ( C. drummondii , C. preissii , C. acuminata , C. arenaria , and C. pyramidalis ). Only Callitris intratropica is a solely tropical species distributed across northern Australia, from the Kimberley to the wet tropics. Callitris glaucophylla is a well-known element in Australian xeric regions and occurs in all states and territories of the mainland.