Callitriche cyclocarpa Hegelmaier (1868: 116)

Lansdown, Richard V., 2022, The genus Callitriche (Plantaginaceae, Callitricheae) in Australasia and Oceania, Phytotaxa 547 (3), pp. 243-284 : 255-256

7. Callitriche cyclocarpa Hegelmaier (1868: 116) .

Type: — AUSTRALIA. VICTORIA, Yarra Yarra, s. dat., F. Mueller s.n. (holotype: STU83917; isotype: MEL224504)

Description: —Stem and leaf scales present. Leaf bases connate. Lingulate leaves 11.4–18.4 mm long × 0.5–0.7 mm wide, expanded submerged or floating leaves spathulate, 5.5–7 mm long × 2.4–2.9 mm wide; venation complex, secondary veins with abundant curved branches joined only at one end, petiole 1.4–3.2 mm long; leaves of terrestrial plants unknown. ♀ flowers only in axils of lower leaves, ♂ and ♀ together in axils of upper leaves. Bracts caducous 0.6–1 mm long. Styles erect, deciduous c 1.5 mm long. Filament ≤ 2 mm long, much longer than fruit; anthers, 0.2– 0.3 mm long × 0.3–0.4 mm wide, number of locules unknown; pollen yellow. Fruit strumose, occasionally shortly pedicellate, more or less isodiametric, dark brown when mature, 0.8–0.9 mm long × 0.8–0.9 mm wide, narrowly winged throughout.

Illustrations: — Figures 12 (a–b) and 12A(a–c) in Mason (1959). Fig. 1g .

Recognition: — C. cyclocarpa can be distinguished from all other Callitriche species in the region by the fruit which are large, blackish, ± isodiametric or wider than high and winged, combined with both ♀ and ♂ flowers at least in upper axils. It most closely resembles C. umbonata from which it can be distinguished by the fruit of that species which are typically higher than wide and the venation which is typically complex in C. cyclocarpa but relatively simple in C. umbonata .

Distribution: —Native. Callitriche cyclocarpa is endemic to Australia where it has a scattered distribution in Victoria with a small number of records in each of New South Wales and South Australia ( Mason 1959, Willis 1972, Jeanes 1999) ( Fig. 7 ).

Habitats and Ecology: —Confirmed specimens of C. cyclocarpa are all aquatic plants with apical leaf rosettes and many with linear lower leaves. It will occur in water at least 40 cm deep, as well as on drying mud of rivers, pools, drainage ditches and wet tracks, typically set in Eucalyptus camaldulensis or occasionally E. microcarpa (Maiden) Maiden (1923: 438) woodland and at least once in a freshwater coastal Melaleuca von Linné (1767: 507 , 509) wetland. It has been recorded growing with species such as Damasonium minus (R.Br.) Buchenau (1871: 20) , Lilaeopsis sp. , Muehlenbeckia florulenta Meisn. (1856: 116) and Nitella (C.Agardh ex Bruzelius) C. Agardh (1824: 124) sp. in water bodies, as well as with Paspalidium jubiflorum along river banks and Austrodanthonia setacea (R.Br.) H.P. Linder (1997: 273) and A. caespitosa (Gaudich.) H.P. Linder (1997: 271) on less-frequently inundated ground. There is no information available on the elevation at which this species occurs.

Conservation Status: —The information available is not adequate to assess the conservation status of the species and it is therefore classed as Data Deficient ( IUCN 2012). Prior to synonymisation with C. umbonata , C. cyclocarpa was classed as Vulnerable in the state of Victoria ( Threatened Species Scientific Committee 2008). It was removed from the Environment Protection and Biodiversity Conservation Act 1999 list of threatened species on 16 September 2015 ( Department of the Environment 2020) but the need for it to be reinstated should be considered.

Notes: — Callitriche cyclocarpa was subsumed within C. umbonata Hegelm. (1867: 20) based on the suggestion that fruits of the type of C. cyclocarpa are immature and on variability of fruit in C. umbonata ( Bean 2007: 548) . However, comparison of more than 50 mature fruit of both species ( Fig. 8 ) shows that although there is a slight overlap, fruit size differences are generally consistent. In particular, the fruit of C. umbonata are typically longer than wide and generally longer than the fruit of C. cyclocarpa . Although based on a relatively small sample and entirely based on herbarium material, there are other differences between the two taxa, for example, the lingulate leaves of C. cyclocarpa are typically longer, while expanded leaves show complex venation compared to fairly simple venation in C. umbonata . There are also differences in the length of the style, filament and possibly the anther, although more information is needed based on living material to clarify this. It appears that in C. cyclocarpa female flowers start to develop before the males, so the lower nodes typically only have female flowers in the axils, but the upper nodes have both male and female flowers in one or both axils. It also appears likely that C. cyclocarpa can flower under water. As with many Callitriche species in Oceania, there is a need for detailed morphological research, based on living material.

Selected specimens examined: — AUSTRALIA: NEW SOUTH WALES. Macquarie Marshes, 31 August 2007 , M. B. Thomas 3721 & R. M. Dowling ( BRI AQ791575) . SOUTH AUSTRALIA. Mount Monster Conservation Park , 4 October 1988 , J. H. Browne 167 ( AD 98846132 ); Telowie Gorge Conservation Park , 10 October 1989 , R. Bates 20482 ( AD 98940227 ); Mt Remarkable National Park , October 2003 , R. Bates 61233 ( AD 155209 ) . VICTORIA. Swan Hill, 3 September 1974 , N. Macfarlane 833 ( MEL 545200 ); Edwards River , October 1895 , F. von Mueller s.n. ( MEL 2246477 ); Loch Garry State Forest , 10 October 1980 , G. K. Patterson 565 ( MEL 626737 ); Dowdle Swamp Wildlife Reserve , 12 September 1985 , A. C. Beauglehole 80337 ( MEL 717648 ); Hawkesdale , December 1903 , H. B. Williamson s.n. ( NSW 935610 ); Spring Vale , September 1910 , A. J. Tadgell s.n. ( MEL 224507 ); Hawkesdale , November 1903 , Williamson s.n. ( MEL 2247539 ); Mount Pilot Multi-Purpose Park , 6 September 1981 , A. C. Beauglehole 88300 & P. Ward ( MEL 717646 ); Wail State Forest Reserve , 15 October 1986 , A. C. Beauglehole 86116 ( MEL 717652 ); Kooyoora - Melville Caves State Park , 24 October 1981 , A. C. Beauglehole 69440 ( MEL 597290 ); Hawkesdale, November [19]03 , H. B. Williamson s.n. ( MEL 224508 ); Glenorchy , 9 September 1961 , A. C. Beauglehole 6772 ( MEL 2246472 ); Barmah Regional Park , 20 November 1985 , A. C. Beauglehole 82406 ( MEL 2299326 ) .

Figures

FIGURE 1. Fruits of Callitriche in Oceania and Australasia: a—C. antarctica, b—C. aucklandica, c—C. brachycarpa, d—C. brutia, e—C. capricorni, f—C. chathamensis, g—C. cyclocarpa i face on and ii end on, h—C. cycloptera, i—C. deflexa, j—C. fuliginea.

FIGURE 7. The distribution of confirmed specimens of C. cyclocarpa

FIGURE 8. Dimensions of fruit of C. cyclocarpa and C. umbonata, numbers in brackets indicate the number of fruit measured, the line shows equal length and width

FIGURE 12. The distribution of specimens of C. muelleri based on data held on AVH (inset: Chatham and Kermadec Islands)