Stephen B. Johnson
Department of Primary Industries, Locked Bag 6006, Orange New South Wales 2800, Australia.
Lyn A. Craven
Australian National Herbarium, CSIRO Plant Industry, GPO Box 1600, Canberra Australian Captial Territory 2601, Australia.
Cite this article as:
Johnson, S.B. and Craven, L.A. (2013). Identification of, and further evidence for the indigenous status of two weedy bladder ketmia species (Hibiscus trionum complex, Malvaceae); and the search for Australia’s inland sea. Plant Protection Quarterly 28(2), 50-6.
The species known as Hibiscus trionum L. is extremely variable and is best described as a species complex. A recent taxonomic revision of Australasian members of the complex suggested three indigenous species occur. This includes the two troublesome summer cropping weeds, H. verdcourtii Craven, wide or broad leaf bladder ketmia, (previously H. trionum var. vesicarius (Cav.), Hochr.) and H. tridactylites Lindl., narrow leaf bladder ketmia, (previously H. trionum var. trionum). This paper presents information to improve the identification and management of these species. Importantly, after examining early European accounts of the area, the paper presents further evidence that both species are indigenous, contributing information that will aid a world-wide taxonomic revision of the complex. These same accounts resulted in an unexpected conclusion about the search for the “inland sea”, the focus of some early European exploration in eastern Australia. While these explorers failed to find this sea, and correctly concluded it did not exist as a permanent entity, they probably did so on erroneous evidence. Large volumes of shallow, slow moving water still inundate the plains surrounding the Barwon, Macquarie and Darling rivers during flooding and these occurrences form one of the likely explanations for such stories.
The species known worldwide as Hibiscus trionum L. (Malvaceae) and commonly known as bladder ketmia in Australia, is extremely variable and requires a significant taxonomic revision (Johnson et al. 2004, Craven et al. 2011). In Australasia, three indigenous and one naturalised species of the H. trionum complex are currently recognised (Craven et al. 2011). This paper presents further evidence that suggests two of the recently circumscribed H. trionum species are indigenous to Australia. In doing so it contributes information that will aid the eventual world-wide taxonomic revision of the complex. Secondarily, since both of the recently circumscribed species are significant weeds in summer cropping systems in eastern Australia (Johnson et al. 2002, Johnson 2006), the information in this paper aims to improve the identification, and hence management, of these taxa. Accordingly, this paper is a companion to an earlier taxonomic revision paper of the species complex in Australasia (Craven et al. 2011). Finally, in examining the earliest European accounts of exploration in this area to ascertain the origins of both species, we contend that had the explorer Thomas Mitchell explored far enough south and west he would have encountered, what Charles Sturt had earlier discovered, inundation evidence of an “inland sea”, although not of the scale of that supposed andpublished by Thomas J. Maslin in his 1827 book ‘The friend of Australia (SL NSW 2012).
Confusion surrounding the taxon bladder ketmia (Hibiscus trionum)
While the species complex known as bladder ketmia (Hibiscus trionum L.) is now more commonly treated in Australian floras as being naturalised, for example Mitchell (1981), Jessop (1986) and Walsh (1996), some authors have historically regarded it as being indigenous, for example Bailey (1899), Blackall and Grieve (1956), Cunningham et al. (1981) and Mitchell (1981). In other cases, the variety formerly known as H. trionum var. trionum has been regarded as naturalised, while the former H. trionum var. vesicarius (Cav.) Hochr. has been treated as indigenous, for example Wheeler (1987), Mitchell and Norris (1990) and Walsh (1996). Further compounding the confusion, only some guides used for field identification recognise variability between the taxa (e.g. Wilson et al. 1995), while other publications used for taxonomic purposes (e.g. Stanley and Ross 1986) and for identification (e.g. Cunningham et al. 1981, Auld and Medd 1987) fail to make any distinctions, despite extensive herbarium collections available at the time of their publication (Johnson et al. 2004).
The variety formerly known as H. trionum var. trionum (Mitchell and Norris 1990, Johnson 2003, Johnson et al. 2004, Johnson 2006, Figure 1), is an annual weed of summer cropping systems, particularly of cotton (Gossypium spp.), and grain sorghum (Sorghum bicolour (L.) Moench), but also of other cereal crops, and in disturbed areas. Although annual, it persists into winter in sheltered situations such as in crop and fallow stubble, or growing in surrounding vegetation (Johnson 2003, 2006). This taxon, commonly called narrow leaf bladder ketmia in the cotton industry (Johnson et al. 2004), is now H. tridactylites Lindl. (Craven et al. 2011).
The variety formerly known as H. trionum var. vesicarius (Cav.) Hochr. (Mitchell and Norris 1990, Johnson 2003, Johnson et al. 2004, Johnson 2006, Figures 2 and 3) is also a weed of summer cropping systems, but is killed by frost (Johnson 2003, 2006). This taxon is commonly called wide or broad leaf bladder ketmia in the cotton industry and is now H. verdcourtii Craven (Craven et al. 2011). Southerly populations of H. verdcourtii have yellow or pallid colouring at the base of their petals (Figure 2), while more northerly populations have a strong red basal petal spot (Figure 3) (Johnson et al. 2004, Craven et al. 2011).
A third species, H. richardsonii Lindl., occurs in coastal New South Wales and the North Island of New Zealand (Craven et al. 2011). In spite of its distinctive morphology, the species has been included in H. trionum by Australian botanists. Hibiscus richardsonii is rare, and potentially highly threatened, in both New South Wales and New Zealand. It has never been recorded as being weedy and appears to be susceptible to alteration of its preferred habitat. Throughout much of its previous range, in New South Wales at least, it probably now is extinct.
Hibiscus tridactylites and H. verdcourtii – weedy characters
Both Hibiscus tridactylites and H. verdcourtii have biological characteristics that contribute to their success as cropping weeds. These characteristics include: successive seedling flushes after rainfall or irrigation events throughout spring, summer and autumn; rapid and competitive plant growth, often with the formation of dense stands; large seed production (e.g. 2 000–16 000 seeds per plant); and relatively long seed longevity and dormancy in the soil (Johnson 2003, Johnson et al. 2004).
Historically, there have been difficulties in controlling H. tridactylites and H. verdcourtii in cotton crops because of the restricted range of herbicides available to treat successive seedling flushes and to avoid crop injury (Johnson et al. 2004). These problems have lessened with the introduction of two additional weed management packages in that industry. The first, that of Roundup Ready Flex® cotton, allows up to four applications of Roundup Ready® herbicide (690 g kg−1 glyphosate as a mono-ammonium salt), while the second, Liberty® Link cotton, allows up to four applications of Liberty® 200 herbicide (200 g L−1 glufosinate-ammonium), over the top of any one cotton crop (Johnson 2003, G. Charles personal communication). Both herbicides are registered for the control of “bladder ketmia”. In addition, these Hibiscus species have differential tolerances to at least two other active herbicidal ingredients, that is bromoxynil and trifloxysulfuron sodium. For example, H. tridactylites is more susceptible to bromoxynil than H. verdcourtii (Wallace 2001, Johnson 2003, D. Harvey personal communication). With the exception of the use of Bromicide® 200 (200 g L−1 bromoxynil) in grain sorghum to control “bladder ketmia (Hibiscus trionum)”, neither active ingredient is currently registered for use against the species formerly known as H. trionum (APVMA 2012).
In recent years, races of indigenous genotypes of Fusarium spp. have been associated with disease in eastern Australian cotton growing regions, necessitating changes in management systems and the planting of increasingly resistant crop cultivars (e.g. Kochman 1995, Swan and Salmond 2004). Fusarium genotypes have been isolated from endemic Australian species of Gossypium (Wang et al. 2004, 2006), and it appears these genotypes have been a longstanding component of the Australian mycoflora. The species formerly known as H. trionum (sensu Australian authors) is a symptomless host of the pathogenic races of Fusarium (Allen and Nehl 1997, A. Becerra personal communication), but experimental evidence is lacking as to whether H. tridactylites and H. verdcourtii are equally tolerant of the Fusarium pathogens. Such experimental studies may also present new evidence to confirm the indigenous nature of both H. tridactylites and H. verdcourtii, as indigenous Hibiscus species would be expected to be tolerant of the indigenous pathogens, although this work would require having adequate species from the Hibiscus trionum complex from other countries for comparative purposes. The former species H. trionum (sensu Australian authors) is also an alternative host for other pathogens affecting cotton in Australia, i.e., Alternaria macrospora Zimm. and Verticillium dahliae Kleb. (Johnson and MacKinnon 2002).
Further evidence that H. tridactylites and H. verdcourtii are indigenous to Australia
It has been proposed that both H. tridactylites and H. verdcourtii are indigenous to Australia (Craven et al. 2011). This view is based upon herbarium collections made soon after European settlement in eastern Australia. For example, the explorer Thomas Mitchell collected the plant that was described by Lindley (in Mitchell 1838) as H. tridactylites based on Mitchell’s collection made in 1832 (January 17, Mitchell 1838) “between the Namoi and Gwydir rivers” in New South Wales. A critical examination of Mitchell’s account of finding this species is outlined below, together with evidence used to suggest that the species is indigenous.
In contrast, the location of the first collection of H. verdcourtii in the herbarium of the Royal Botanic Gardens at Kew appears to be from the Narran River in north-western New South Wales (Mitchell 1848). Given the lack of European settlement in the area at the time (see later) and the widespread distribution of H. verdcourtii, which is found throughout western New South Wales, Queensland, the Northern Territory and Western Australia, we consider that the indigenous nature of this species is not in doubt.
The purpose for the journey recorded in Mitchell (1838) was “the exploration of Australia” to substantiate or disprove otherwise details of a large river called the “Kindur”, which when followed in a south-west direction, lead to a sea shore (which some thought was a great inland sea). Overall, the journey described the geography of much of the area that is today known as the north western slopes and plains of New South Wales (see Figure 4). The journey ultimately found that all the watercourses Mitchell examined united in the “Nammoy” (Namoi, although the waters from the two rivers (the “Kindur” and the “Nammoy”) join in what is today known as the Barwon river) and that this river ultimately drained the Peel River which had been named by the explorer John Oxley in 1818 (Oxley 1819).
After setting off from Wellington earlier in 1818, Oxley explored parts of the Macquarie River to the Macquarie Marshes (around what is now known as Mount Foster, slightly north west of present day Warren) and then travelled roughly east from there. In doing so his party crossed the Castlereagh River south of what is today Coonamble, encountered what is today the Warrumbungle Ranges, then travelled across the Liverpool Plains (around Gunnedah), to the Peel River (somewhere near the site of the present day Tamworth). Subsequently, the party crossed what is now known as the Great Dividing Range and followed the Hastings River to its mouth, naming the area Port Macquarie.
As previously stated, Mitchell collected H. tridactylites in 1832 “between the Namoi and Gwydir rivers” (Mitchell 1838). The location of this collection can be determined with somewhat better accuracy than that described above using the latitude recorded in the account and a current day map. In doing so, it is likely that the explorers were somewhere north west of present day Gurley, given that the previous day they were at latitude 29o43’03″S, although they had not crossed what today is recognised as the actual watercourse known as the Gwydir River which runs to the north of Moree. The Gwydir River branches into a number of anabranches to the east and west of Moree with most of the water flowing through the main branch of the Mehi River (all anabranches are collectively labelled as the Mehi River in Figure 4). It is likely that the site where Mitchell encountered H. tridactylites was south west of Moree in an area of several Mehi anabranches, probably north of Moomin creek (which Mitchell named the Kareen), near the current day locality of Mallowa (not illustrated).
We contend that the only inhabitants of the area were members of the Kamilaroi aboriginal nation (Tindale 1974, Gammage 2011). We base the contention that H. tridactylites is indigenous to the area on a number of pieces of evidence as outlined below.
- There is no mention of European settlers, or evidence of settlers camps, tracks, or domesticated animal grazing in the area when the collection was made in 1831 (Mitchell 1838). It is also important to note that Mitchell does not discover evidence of other expeditions to the broad area he explored, nor do previous expeditions mention settlement in the broad area Mitchell explored. For example, the expeditions of:a. Oxley in 1818, which may have been up to 200 km to the south (Oxley 1819);
b. Charles Sturt and Hamilton Hume in 1828/29, along the Macquarie River from Wellington to the Macquarie Marshes; the lower Bogan River (not illustrated but west of the Macquarie River), and along the Darling River to beyond what is now Bourke; and to the lower Castlereagh below what is now Coonamble to its junction with the Macquarie and then the Darling River (Cumpston 1957, Gibbney 1967). These explorations were up to 200 km to the west and south west; and
c. Allan Cunningham in 1827, who explored the Peel River, crossed the Gwydir near what is thought to be Bingara, and then travelled north through the area now known as Warialda and onto the Darling Downs (Anon. 2012, Gwydir Shire Council 2012). The closest Cunningham would have travelled to the area of the collection was at least 100 km to the east.
- As a general point, settlement by Europeans was only authorised in certain areas of what was considered to be Crown Land in the early days of the colony of New South Wales (NSWG, SR 2012). Initially this was in the ‘limits of location’ set by Governor Darling in 1826, which was broadened to an area around Sydney called the nineteen counties in 1829 (bounded by the Manning River to the north, the Shoalhaven River to the south and the upper Murrumbidgee River in the west, (NSWG, SR 2012, Wikipedia 2012)). Despite this, there was “extensive unauthorised settlement” of Crown Lands by 1833 and eventual licensing of these graziers (squatters) under an 1836 Act of Parliament (NSWG, SR 2012). The records indicate that the first of these pastoral squatters settled in 1837 (at Port Macquarie) with no squatter licensing reported in the area of plant collection until after 1849, the closest in geographic location before this being on the Liverpool Plains in 1844.
- In contrast, explorers had frequent contact with members of at least four aboriginal nations: these being the Kamilaroi (in the current day areas of Tamworth, Gunnedah, Narrabri, Moree, Mungindi, Collarenebri and Walgett); the Weilwan (in the lower Castlereagh and Macquarie Rivers); the Kawambarai (in the upper Castlereagh River and mid Macquarie River); and the Wiradjuri (south and south east of what is today Dubbo), (Tindale 1974).
- Although there was no pastoral squatting in the area, there was some other illegal settlement, including by escaped convicts. Having said this, the only settlers mentioned by Mitchell are encountered either east of Tamworth (and the Peel River – an old stockman and his wife), and at Wallamoul on the Peel River (around two miles from where Oxley had crossed the river, somewhere near present day Tamworth). Here, a Mr Brown and associated stockmen maintained a station with around 1600 cattle (Mitchell 1838).
- It appears that only after Mitchell had explored the areas to the west of Tamworth along the Peel and Namoi Rivers that Mr Brown followed in his footsteps. In particular, Mitchell (1838) records meeting with Mr Brown in late February 1832, west of Tamworth, as Mr Brown came to investigate whether some of his missing cattle could be found. This meeting followed the return to Mr Brown of an aboriginal guide of Mitchell’s. This guide informed Mr Brown of the discovery of a stockyard (see below). This information lends further evidence to the conclusion that the areas significantly west and north west of Tamworth had not been settled by Europeans at the time of Mitchell’s exploration.
- Having said this, it is known that one white man, the bush ranger George Clarke, alias ‘The Barber’, had lived in this area with the Kamilaroi people: a bush ranger is an escaped convict or robber living in the wilderness or bush. Clarke’s account of the “Kindur”, a large river which when followed in a south western direction lead to a “sea shore” is at least one reason why Mitchell’s expedition was mounted.
- Mitchell found considerable evidence that Clarke had been living with the Kamilaroi people near what is today Boggabri, around 100 km south/south east of the area of collection. For example “a very large stock-yard” with the remains of a house, huts of aboriginal people and a “great abundance” of cattle bones, were identified by Mitchell’s aboriginal guide as belonging to Clarke. This area was beside a large lagoon of water and was known as “Tangulda” by the Kamilaroi people. Tangulda is said to be named after a striking outcrop of rocks near the lagoon (Narrabri Shire Council 2012). Today, the lagoon is known as Barber’s lagoon and can be found around 5–10 kilometres directly east of Boggabri.
- It appears that George Clarke had been stealing cattle from Mr Brown (Mitchell 1838). This was substantiated by Mr Brown after he examined brands on cattle hides near the stockyards at the ‘Tangulda’ camp in late February 1832. In saying this, it is possible that cattle stealing from other settlers then living on the Liverpool Plains may also have occurred.
- If the cattle stolen were not killed to eat immediately once they were brought back to the ‘Tangulda’ camp, it is possible that they would have been allowed to graze on the surrounding plains. While it is possible that they may have ranged up to 100 km from Boggabri to the site where the plant was found, it is not altogether certain.
- Based on one of Clarke’s observations related to Mitchell, we contend that it is clear that the bushranger had traversed much of the surrounding plains west and north of his ‘Talgunda’ camp. This conclusion is in stark contrast to that of Mitchell (1838, see Postscript). For example, while Clarke is aware of the Nandewar Ranges (which Mitchell notes), Mitchell disregards information that the “Kindur”, a large river, when followed in a south west direction lead to a sea. This large river could have been the Gwydir River which Cunningham had earlier crossed up stream, or the Barwon River (which the Kamilaroi people called the Karaula) which Mitchell later traced south west from its junction with the Gwydir River.
- Mitchell collected the plant from an area of open and elevated country where “most of the ground was covered with hibiscus (with red stalk and small flower) which grew to a height of twenty inches” (Mitchell 1838). Such a large area indicates that the population had been present for at least several years, even when the prolific seed production of H. tridactylites is accounted for (Johnson et al. 2004).
The most significant piece of evidence that may contradict the conclusion is that Mitchell fails to mention the plant in other areas throughout his exploration accounts (e.g. Mitchell 1838 and 1848) and that mention of such a common species may have been expected. To explain this, Mitchell often only records single references to many plant species, not just H. tridactylites, the exceptions being of the dominant tree species that he observed. Although the records are silent on this point, it would be sensible to assume that Mitchell would have observed multiple new (but previously observed) species at multiple locations, but that each location of such new species is only very rarely recorded.
It is also apparent that species such as H. tridactylites are classic ‘ruderal’ or colonising species, that is, plants that are fast-growing, short-lived and highly reproductive (Grime 1977). Such species are found in situations that are highly disturbed. While it initially appears that H. tridactylites was growing in relatively undisturbed grassy woodlands (Keith 2004) that may have only been strategically burnt (Gammage 2011), it is important to note that the area of collection is likely to have been between significant anabranches of the Mehi/Gwydir River (these are not illustrated in Figure 1) and subject to persistent but periodic inundation from flooding events. Ruderal species are common in these environments, as they are in nearby cotton production areas today (e.g. Johnson and Hazlewood 2002).
Thomas Mitchell has been recognised as a particular observer of the country and people he surveyed (e.g. Gammage 2011). In contrast to this commonly held view, when forced to return from the extent of his exploration on the Barwon, he stated “we had at least accomplished the main object of the expedition, by ascertaining that there was no truth to the bushranger’s report, respecting the great river”, and, of course, the inland sea. It is on this point we contend Mitchell is mistaken. He fails to have understood that, at that time of his exploration, the low flowing Gwydir and the anabranches he saw around Moree formed part, with the surrounding plains, of a very large river in flood. Furthermore, the Barwon River he later encountered was similar during flooding (S. Johnson, personal observations).
Having decided that the Barwon River was in fact the Darling River (rather than just one of the upstream tributaries of the Darling), Mitchell terminated his journey somewhere south west of present day Collarenebri. He rightly expected waters from the Namoi and the Castlereagh Rivers to join this river over the next 150 km, but did not appear to have connected this with the fact that the river he was on would join the Macquarie River north west of Carinda and north of the Macquarie Marshes.
Thomas Mitchell correctly concluded that there was no inland sea, a fact also later confirmed by other explorers, (e.g. Stuart (1865)), but probably did so on erroneous evidence. During flood events and in high river flow periods, it is likely that the water coming from the Macquarie Marshes would inundate large areas west of current day Walgett (and north of what is today Carinda) forming what Clarke claimed was a sea, or at least a large volume of shallow very slow-flowing water. This would explain why Clarke, after examination by Mitchell and the Acting Governor in prison “persisted in his story of the river”.
Thomas Mitchell’s account of the country they traversed being “very eligible in many parts for the formation of grazing establishments” resulted in both sheep and cattle grazing in the area soon after his explorations and it becoming “an important addition to the pastoral capabilities of New South Wales” for many decades before being partly succeeded by irrigated and dryland cropping today.
Two taxa within the species complex Hibiscus trionum are problematic in summer cropping systems in eastern Australia. The first, H. verdcourtii, wide or broad leaf bladder ketmia (previously H. trionum var. vesicarius) has at least two forms with southern populations having a yellow or pallid colour at the base of their flower petals while more northern populations having a strong red basal spot. The indigenous nature of this species to Australia is widely accepted.
There is increasing evidence that the second species, H. tridactylites, narrow leaf bladder ketmia (previously H. trionum var. trionum), is also indigenous to Australia. The species was collected upon European exploration of the area, and hence before European settlement. Eleven points of evidence are examined based on early accounts of Europeans in the area. All confirm the indigenous nature of the species. Further, these accounts reveal another detail about the early exploration of eastern Australia and the search for a permanent “inland sea”. While the explorer Thomas Mitchell concluded correctly that there was no inland sea, he probably did so based on erroneous evidence. We contend this careful observer failed to understand that large volumes of shallow, very slow moving water inundated the plains south west of where he explored along the Gwydir and Barwon rivers and it is likely an early convict to whom Mitchell conversed was correct in claiming these periodically inundated areas were an intermittent “inland sea”.
The authors are particularly grateful to the following people for information and corrections for this paper: Chris Anderson, Augusto Becerra, Graham Charles, Dennis Harvey and Richard Roger. Special thanks go to Udai Prahan, Spatial Information Systems Officer with the New South Wales Department of Primary Industries, Orange for preparing Figure 4. We thank the peer reviewers and independent editor for their comments which have improved the paper.
SBJ is particularly grateful to Mrs Frances Spora (nee O’Brien) who has spent many hours explaining the ecology and dynamics of vegetation and flooding in and around her childhood home at ‘Yahgunyah’ in the eastern Macquarie Marshes.
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