Cycas Terryana Piforst. (Cycadaceae)

Cycas terryana P.I.Forst. (Cycadaceae), a new species from central Queensland Paul I. Forster Summary Forster, P.I. (2011). Cycas terryana P.I.Forst. (Cycadaceae), a new species from central Queensland. Austrobaileya 8(3): 356–363. A new species of Cycas from the Broadsound and Connors Ranges in central Queensland is described, illustrated and diagnosed as C. terryana P.I.Forst. It is known from five populations in an area of occurrence of approximately 800 km² and does not occur in any conservation reserves. A conservation status of Vulnerable based on the IUCN criterion of D2 is recommended for the species. Key Words: Cycadaceae, Cycas, Cycas terryana, Australia flora, Queensland flora, new species, taxonomy, identification key, conservation status P.I.Forster, Queensland Herbarium, Department of Environment & Resource Management, Brisbane Botanic Gardens, Mt Coot-tha Road, Toowong, Queensland 4066, Australia. Email: paul.forster@ derm.qld.gov.au Introduction The genus Cycas L. is speciose in Australia hybridism’ hypothesis remains to be tested with 28 species recognised (Hill 1998, 2004). using molecular markers (e.g. haplotype The species generally occur in well defined, networks [Schaal & Olsen 2000]) and remains geographically discrete areas in few (in several merely as a plausible supposition in some instances one) to many populations. Botanical cases. Alternative hypotheses are that these exploration in Queensland continues to populations are merely variations of more reveal previously undocumented populations broadly defined species or in some instances of Cycas; such a case pertains to several represent discrete taxa. populations of plants in the area southwest of Hill’s propensity for designating a large St Lawrence and northwest of Marlborough in number of Cycas populations as hybrids the Broadsound and Connors Ranges. or examples of introgression was probably Hill (1992) was of the opinion, albeit influenced by his work on eucalypts (where without supporting evidence, that this this is widespread and by comparison well material represented a zone of hybridism documented with genetic studies) and his (“intergrading populations”) between Cycas mentoring by L.A.S.Johnson who together media R.Br. and C. ophiolitica K.D.Hill. with Lindsay Pryor was a keen supporter This hypothesis was developed further of the ‘phantom’ hybrid population concept (Hill 1996: 3), viz. “these [populations] are (Pryor 1951; Pryor & Johnson 1971; Parsons & morphologically intermediate between the Kirkpatrick 1972; Johnson 1976; Kirkpatrick putative parent species and also show the & Potts 1987). Eucalypts are bisexual, high degree of variability to be expected from often promiscuous outbreeders with non Mendelian segregation in second and later specialist pollinators and appear to be readily generations”. Such introgressed populations dispersed; hence, the potential for hybrids were considered to occur throughout the where different taxa adjoin is high, although range of the genus in Australia (Hill 1996) recorded instances are relatively low (Griffin and elsewhere (e.g. Hill 1994, 2008; Hill et al. et al. 1988). Populations of hybrid individuals 2004), in some instances between species that may lead to extinction of the parental species he classified in different series. This ‘multiple via genetic pollution, although in many cases the progeny are sterile or with reduced viability (Levin 2000). Alternatively, these Accepted for publication 18 July 2011 populations may in time lead to separate speciation events once fertility is restored Forster, Cycas terryana 357 (e.g. via allotetraploidy) and genetic change or others that he examined and determined via selection or genetic drift occurs (Levin as such. There are now five populations of 2000). these plants known and perhaps more in what is largely a botanically unexplored part of The situation in Cycas is quite dissimilar, central Queensland. insomuch as the plants are dioecious, require pollination by insects (in variations of a Neither of the putative parental species mutualistic relationship) and perhaps wind in have populations that are particularly combination (Kono & Tobe 2007), polyploidy geographically close to the Broadsound and is unknown (Gorelick & Krystle 2011), and Connors Ranges plants. Hill (1996) vaguely distribution of the populations are limited stated that the hybrid populations were by dispersal (Forster 2007). As noted by “wherever different species grow in relatively Hill (1992) it is perhaps unlikely that strong close proximity”. The closest population of genetic barriers to cross pollination between Cycas media is c. 9 km to the northeast (in different taxa exist and so the only real different habitat and geology) and the closest barrier to hybridism/introgression is isolation population of C. ophiolitica some c. 45 km to in geographic space. Populations of Cycas the east of the overall area of occupancy for the and other Australian cycads are rare in the five populations. The southern populations of landscape for the above reasons, quite unlike Cycas media are predominantly coastal and the situation with most eucalypts. Johnson occur on substrates derived from basalts, finer (1959, 1961) actively promoted the concept of grained granites or stabilised sand masses. widespread hybridism in cycads, especially for The northern populations of Cycas ophiolitica Zamiaceae (Macrozamia) species, although are restricted to serpentinite substrates. By some of his examples are merely juveniles of comparison the Broadsound and Connors much larger adults (e.g. M. lucida × M. moorei; Ranges plants occur well inland in the ranges juveniles of what is now known as M. johnsonii on substrates derived from heavily weathered D.L.Jones & K.D.Hill) or represented discrete porphyritic granites. taxa that he was not aware of. Speciation in Cycas and Macrozamia is perhaps most These populations of Cycas may likely to occur via genetic drift in isolated well have originated from mixing of the populations, rather than genetic selection per ancestral lineages of both C. media and se (Gorelick 2009). This is reflected in the C. ophiolitica as postulated by Hill, with occurrence of similar appearing taxa, often in speciation following the initial hybridism and a geographic replacement series of allopatric subsequent geographic isolation. However, the populations. This can be interpreted as an situation could well be much more complex indication of both continuous and incomplete than this and reflect multiple instances of speciation in a non-adaptive radiation where fragmentation and integration of populations the inter-relationship between environment driven by climatic changes since the glacial and morphology is unclear (Savolainen & cycles of the Pleistocene. This hypothetical Forest 2005) and in cycads is probably driven pattern of change has been actively promoted mainly by fragmentation, rather than radical as one of the main drivers of speciation in differences in habitat specialisation (cf. Linder Mexican cycads (Vovides et al. 2003) and 2003). Either way, the tempo of speciation is similar reproductive and dispersal biology likely to be slow given the long time period of the Australian cycads may infer similar between germination and individuals reaching patterns of allopatry (Forster 2004). maturity, together with slow turnover of Given that the recorded populations of individuals within populations. these Cycas are disjunct over an area of With regard to the so called Cycas media occurrence of at least 800 km², it is likely – C. ophiolitica intermediates south of St that the hypothesised speciation event is well Lawrence, Hill (1992) was probably only aware advanced with subsequent fragmentation of two populations based on his collection following an initial introgression. It is (Hill 3788 & Stanberg) and that of Hind 2878, unlikely that these populations are any less fit 358 Austrobaileya 8(3): 356–363(2011) than the core Cycas media or C. ophiolitica leaflets inserted at 20–50º to the rhachis, the populations and to all extents they appear rhachis usually terminated by paired leaflets, to exist and operate much like any other tomentose; petiole 17–30 cm long, 7–15 mm healthy cycad populations. If of hybrid origin, diameter, dull olive grey-green, with 4–40 then they probably commenced as a neutral short teeth (pinnacanths) 1.5–2 mm long and hybrid zone with genetic compatibility and spaced 8–17 mm apart, sometimes spineless. superficially similar habitats, although such Leaflets 184–320 per leaf, 7–10 mm apart, zones are usually in close proximity to the being evenly spaced in lower half of leaf, putative parental species (Levin 2000) which then becoming more interleaved and more is no longer the case here. Whatever the origin, strongly keeled in upper half of leaf, brittle, these populations possess character states that margins recurved; median leaflets at 25–45º enable them to be distinguished from both to the rhachis, 105–230 mm long, 5–7 mm Cycas media and C. ophiolitica; hence, they wide, green-grey with fawn-tan bloom when are described below as a new species. The young; weakly convex in cross section, hypothesised species origin is also relevant decurrent for 5–7 mm, up to 13 mm at base for speciation elsewhere in Cycas and other of leaf. New growth densely tomentose with genera of cycads, particularly Macrozamia pale cream-fawn indumentum, glabrescent. Miq. from Australia (Forster 2004), Cataphylls pungent, linear, 8–12 cm long, Encephalartos Lehm. in Africa (Vorster

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