{{Short description|Australian / New Zealand native plant species}} {{Speciesbox | name = Sand bidibid | image = Acaena-pallida-2.jpg | image_caption = | genus = Acaena | species = pallida | authority = (Kirk) Allan | range_map = File:Acaena pallida distribution map from Atlas of Living Australia.png | range_map_caption = Acaena pallida distribution map from Atlas of Living Australia }}
'''''Acaena pallida''''', commonly known as the '''sand bidibid''', '''sand piripiri''',<ref name="NZ Flora">{{cite web |title=''Acaena pallida'' (Kirk) Allan |url=https://www.nzflora.info/factsheet/Taxon/Acaena-pallida.html |website=Flora of New Zealand |access-date=15 March 2026}}</ref>''' pale bidibid''',<ref name="Dicot Key">{{cite web |author1=University of Tasmania |title=Acaena pallida |url=https://www.utas.edu.au/dicotkey/dicotkey//ROS/sAcaena_pallida.htm |website=Key to Tasmanian Vascular Plants |access-date=15 March 2026}}</ref> or '''dune buzzy''',<ref>{{cite book |last1=Wapstra |first1=Hans |last2=Wapstra |first2=Annie |last3=Wapstra |first3=Mark |last4=Gilfedder |first4=Louise |title=The Little Book of Common Names for Tasmanian Plants |date=2005 |publisher=Department of Primary Industries, Parks, Water and Environment, Government of Tasmania |isbn=0 7246 6365 7 |pages=8, 65 |url=https://nre.tas.gov.au/Documents/Common_names_booklet.pdf}}</ref> is a prostrate, herbaceous plant in the Rosaceae family that is native to New Zealand and south-eastern Australia, including Tasmania.<ref name="NZPCN">{{cite web |last1=Ward |first1=MD |title=Acaena pallida |url=https://www.nzpcn.org.nz/flora/species/acaena-pallida/ |website=New Zealand Plant Conservation Network |access-date=15 March 2026}}</ref> It lives in coastal areas, primarily on sand dunes.<ref name="NZPCN" />
==Description==
''Acaena pallida'' is a small perennial, herbaceous plant with a prostrate, stoloniferous growth habit. The main stems reach up to 1m in length and are usually 3-4mm in diameter.<ref name="NZ Flora" /><ref name="Dicot Key" /> Younger stems are green and densely hairy, while older stems are tough and woody with dark brown bark, and may be as thick as 10mm.<ref name="Macmillan">{{cite journal |last1=Macmillan |first1=B.H. |title=''Acaena pallida'' in Tasmania and New South Wales, Australia |journal=Papers & Proceedings of the Royal Society of Tasmania |volume=124 |page=53-56 |url=https://eprints.utas.edu.au/14662/10/Macmillan__Acaena_pallida.pdf |issn=0080-4703}}</ref> Erect stems reach up to 15cm in height.<ref name="NZ Flora" /> Stolons will root at the nodes, allowing the plant to expand and form a loose, trailing mat.<ref name="Growth & Reproduction">{{cite journal |last1=Lloyd |first1=Kelvin M. |last2=Lee |first2=William G. |last3=Wilson |first3=J. Bastow |title=Growth and reproduction of New Zealand Acaena species in relation to rarity and commonness |journal=New Zealand Journal of Ecology |date=2002 |volume=26 |issue=2 |pages=149-160 |url=https://www.jstor.org/stable/24055317 |access-date=16 March 2026}}</ref>
The leaves are 2.5-12cm in length, divided into 9-15leaflets, 45-100mm long, with many blunt teeth.<ref name="NZ Flora" /> The upper surface of the leaf is glossy green with a wrinkled appearance.<ref name="NZ Flora" /><ref name="Acaena Key">{{cite journal |last1=Lloyd |first1=Kevin |title=A Key and notes for Acaena (Rosaceae) in New Zealand |journal=Botanical Society of Otago Newsletter |date=2001 |issue=25 |pages=10-14 |url=https://bts.nzpcn.org.nz/site/assets/files/24276/2001_bso_newsletter_volume_25_10-14.pdf |access-date=15 March 2026}}</ref> The lower surface is hairy and pale green to white, with epicuticular wax.<ref name= "Macmillan" />
thumb|A young ''Acaena pallida'' inflorescencethumb|''Acaena pallida'' inflorescence at fruiting
The inflorescence scape is 7-18cm long and hairy, terminating in a spherical inflorescence head of 80-90 florets. The head is approximately 10-12mm in diameter at flowering, reaching 25-40mm at fruiting.<ref name="NZ Flora" /><ref name="NZPCN" /> The individual florets consist of: 4 sepals, ovate to oblong and hairy underneath; 2 stamens, with white anthers; and 1 style, which is white. The florets have no petals. The fruit are conical and hairy, becoming dry and brown at maturity, with 4 barb-tipped spines on the top, and 1-2 much shorter subsidiary spines lower down on the fruit. The 4 top spines are red to light brown and 10-20mm long.<ref name="NZPCN" /><ref name="Macmillan" />
Information on phenology varies between sources. Flowering reportedly occurs from October through to January, and fruiting from October-December through to April-May.<ref name="NZPCN" /><ref name="NZ Flora" /> However, Lloyd et al. (2002) found production of new inflorescences to begin in October and continue for 32 weeks, suggesting flowering can occur through to April/May.<ref name="Growth & Reproduction" />
===Differentiation from ''Acaena novae-zelandiae''===
''Acaena pallida'' is similar in appearance to the more common ''Acaena novae-zelandiae'', which can also be found in dune habitats alongside ''A. pallida''.<ref name="Dicot Key" /><ref name=NZPCN /> New leaves of ''A. novae zelandiae'' can be deceptively glossy/shiny on the upper surface.<ref name=NZPCN /> However, several differences can be used to distinguish the species. ''A. pallida'' is larger in almost all of its features: stems 3-4mm wide, instead of 1.5-2mm; leaves <100mm, compared to <60mm; leaflets 6-30 × 3-13 mm rather than 4-17 × 2-10 mm; capitulum <4cm in diameter instead of <3.5cm.<ref name="NZ Flora" /><ref name="NZPCN" /><ref name="Macmillan" /><ref name="NZ Flora - A. novae-zelandiae">{{cite web |title=''Acaena novae-zelandiae'' Kirk |url=https://www.nzflora.info/factsheet/Taxon/Acaena-novae-zelandiae.html |website=Flora of New Zealand |access-date=16 March 2026}}</ref> ''A. pallida'' fruit have 1-2 shorter subsidiary spines below the 4 main spines, while ''A. novae-zelandiae'' fruit have none. The underside of ''A. pallida'' leaves is more densely hairy, with more epicuticular wax.<ref name="Macmillan" /> The leaf rachis of ''A. novae-zelandiae'' is generally redder and less hairy than ''A. pallida''.<ref name="NZPCN" />
==Evolution and taxonomy==
===Phylogeny and biogeography of ''Acaena''===
''Acaena'' is currently believed to be a paraphyletic genus, with ''Polylepis'', ''Margyricarpus'', and ''Tetraglochin'' nested within it.
The genus is believed to have originated in Southern Africa, with the earliest known intercontinental dispersal event occurring 11.2 million years ago from South Africa to southern South America (Argentina/Chile). There, it diversified across different habitats, and dispersed to sub-antarctic regions, northern South America, Central America, and California. Long-distance dispersal from South America to New Zealand occurred in two discrete events, around 8.3 and 6.3 million years ago respectively. Further diversification occurred in New Zealand, as well as dispersal from there to Australia, Hawaii and back to South America.<ref name="Phylogeny of Acaena">{{cite journal |last1=Jauregui-Lazo |first1=Javier |last2=Potter |first2=Daniel |title=Phylogeny and Biogeography of ''Acaena'' (Rosaceae) and Its Relatives: Evidence of Multiple Long-Distance Dispersal Events across the Globe |journal=Systematic Botany |volume=46 |issue=4 |pages=998-1010 |doi=10.1600/036364421X16370109698597 |url=https://www.researchgate.net/publication/357364327_Phylogeny_and_Biogeography_of_Acaena_Rosaceae_and_Its_Relatives_Evidence_of_Multiple_Long-Distance_Dispersal_Events_across_the_Globe |access-date=16 March 2026}}</ref>
''Acaena pallida'' is thought to comprise a clade with other New Zealand ''Acaena'' species, with speciation only occurring in the last few million years. The phylogeny within this clade is currently unclear, partly due to the genetic and morphological variability within ''Acaena'' species, as well as the presence of hybrids.<ref name="Phylogeny of Acaena" /> Its highly disjunct distribution within New Zealand may suggest it was once more widespread, but underwent local extinctions, leaving several relict populations. Alternatively, it may be a recent arrival to New Zealand.<ref name="Growth & Reproduction" />
==Habitat and distribution== ===Habitat===
''Acaena pallida'' is a specialist species that grows exclusively in coastal regions, where it is found primarily on sand dunes and in dune swales, and sometimes on fine gravels.<ref name="NZPCN" /><ref name="NZ Native Plants">{{cite web |title=Sand Piripiri |url=https://www.nativeplants.nz/acaena-pallida.html |website=New Zealand Native Plants |access-date=17 March 2026}}</ref><ref name="Dicot Key" /> It favours disturbed, unstable sand, particularly the foredune, and acts as a pioneer species colonizing and stabilizing these areas.<ref name=Macmillan /><ref name="NZ Native Plants" /> It favours open, high sunlight areas with good drainage.<ref name="NZ Native Plants" />
===Distribution===
''Acaena pallida'' is native to New Zealand and south-eastern Australia.<ref name="NZPCN" /> Within New Zealand, it has a highly disjunct distribution. On the North Island, it is present in Wellington Harbour<ref name="Flora NZ vol. 4">{{cite book |last1=Webb |first1=C. J. |last2=Sykes |first2=W. R. |last3=Garnock-Jones |first3=P. J. |title=Flora of New Zealand - Volume IV, Naturalised Pteridophytes, Gymnosperms, Dicotyledons |date=1988 |publisher=Botany Division, D.S.I.R. |location=Christchurch, New Zealand |isbn=0 477 02529 3 |url=https://floraseries.landcareresearch.co.nz/taxa/2724424a-1162-4bae-8941-89db6f5ae2c7 |access-date=15 March 2026 |format=Electronic version}}</ref> and along the north side of Cook Strait.<ref name="Flora NZ vol. 1">{{cite book |last1=Allan |first1=H. H. |title=Flora of New Zealand - Volume 1, Indigenous Tracheophyta, Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones |date=1961 |publisher=PD Hasselberg, Government Printer |location=Wellington |isbn=((0 477 01056 3)) |page=360 |url=https://archive.org/details/floraofnewzealan0001alla/mode/2up |access-date=15 March 2026}}</ref> On the South Island, it is found in the region around Otago Harbour<ref name="Flora NZ vol. 1" /> and at Bluff. It is also found at Mason Bay on Stewart Island,<ref name="Flora NZ vol. 4" /> and on the Chatham Islands.<ref name="NZPCN" />
In Australia, the species is present in Tasmania and southern New South Wales.<ref name="Macmillan" /><ref name="ALA">{{cite web |title=''Acaena pallida'' |url=https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/7834302 |website=Atlas of Living Australia |access-date=17 March 2026}}</ref> It is considered likely to also be present in Victoria.<ref name="Macmillan" /><ref name="VicFlora">{{cite web |title=Acaena novae-zelandiae |url=https://vicflora.rbg.vic.gov.au/flora/taxon/4dc33918-59b1-4f71-9702-928c603f44eb |website=Flora of Victoria |access-date=17 March 2026}}</ref> Several observations have been reported, however are currently still being treated as ''A. novae zelandiae'' until further review is conducted.<ref name="VicFlora" />
It has been introduced to California in the United States of America, where it is considered invasive and has been placed on the California Noxious Weeds List.<ref name="CA Weeds">{{cite web |title=CDFA Weed Pest Ratings and CCR 4500 Noxious Weeds |url=https://www.cdfa.ca.gov/plant/ipc/encycloweedia/pdf/CaliforniaNoxiousWeeds.pdf |website=California Department of Food and Agriculture |page=4 |format=PDF |date=June 22, 2021}}</ref>
==Conservation status==
''Acaena pallida'' has been listed as "At Risk - Declining" in New Zealand since 2017. Coastal dune habitats in the North Island and Chatham Islands where ''Acaena pallida'' can be found have suffered substantial and ongoing degradation since the 2000s.<ref name="Conservation Status NZ">{{cite journal |last1=de Lange |first1=Peter J. |last2=Rolfe |first2=Jeremy R. |last3=Barkla |first3=John W. |last4=Courtney |first4=Shannel P. |last5=Champion |first5=Paul D. |last6=Perrie |first6=Leon R. |last7=Beadel |first7=Sarah M. |last8=Ford |first8=Kerry A. |last9=Breitwieser |first9=Ilse |last10=Schönberger |first10=Ines |last11=Hindmarsh-Walls |first11=Rowan |last12=Heenan |first12=Peter B. |last13=Ladley |first13=Kate |title=Conservation status of New Zealand indigenous vascular plants, 2017 |journal=New Zealand Threat Classification Series |date=May 2018 |issue=22 |pages=8-9, 34 |url=https://www.researchgate.net/profile/Peter-James-Lange/publication/325556614_Conservation_status_of_New_Zealand_indigenous_vascular_plants_2017/links/5b15f0614585151f91fb0ce1/Conservation-status-of-New-Zealand-indigenous-vascular-plants-2017.pdf |access-date=17 March 2026 |publisher=New Zealand Department of Conservation |location=Wellington |format=PDF |issn=2324 1713}}</ref> Contributing factors include destruction of habitat for coastal development, invasion by weeds, increasing recreational use, and coastal erosion.<ref name="Macmillan" /><ref name="Conservation Status NZ" />
It is not considered threatened in Australia.<ref name="EPBC list Australia">{{cite web |title=EPBC Act List of Threatened Flora |url=https://www.environment.gov.au/cgi-bin/sprat/public/publicthreatenedlist.pl?wanted=flora |access-date=17 March 2026}}</ref>
==Ecology==
''Acaena pallida'' has a "guerilla" growth strategy - it foregoes density in favour of rapid lateral expansion of stolons. This strategy is associated with species that like disturbance, allowing the plant to act as a pioneer species and opportunistically colonise newly disturbed areas.<ref name="Growth & Reproduction" />
It functions as a sand binding plant, helping to stabilise sand dunes. Wind-blown sand is trapped by the dense hairs on the stems and the loose mat-like structure of the plant.<ref name="Macmillan" /><ref name="NZ Native Plants" />
The barbed spines present on ''A. pallida'' fruit can attach to animal fur or feathers, or human clothing, helping to disperse seed over longer distances.<ref name="Acaena fruit features">{{cite journal |last1=Lee |first1=William G. |last2=Macmillan |first2=B. H. |last3=Partridge |first3=T. R. |last4=Lister |first4=R. |last5=Lloyd |first5=K. M. |title=Fruit features in relation to the ecology and distribution of ''Acaena'' (Rosaceae) species in New Zealand |journal=New Zealand Joournal of Ecology |date=2001 |volume=25 |issue=1 |pages=17-27 |url=https://www.jstor.org/stable/24056359}}</ref>
In Tasmania, it is commonly found as an understorey component of ''Austrofestuca littoralis'' grassland.<ref>{{cite book |last1=Kirkpatrick |first1=J. B. |last2=Harris |first2=S. |editor1-last=Reid |editor1-first=J. B. |editor2-last=Hill |editor2-first=R. S. |editor3-last=Brown |editor3-first=M. J. |editor4-last=Hovenden |editor4-first=M. J. |title=Vegetation of Tasmania |url=https://www.researchgate.net/profile/Stephen-Harris-4/publication/272795196_Coastal_Heath_and_Wetland_Vegetation/links/55e7951308ae3e1218420fa3/Coastal-Heath-and-Wetland-Vegetation.pdf |access-date=17 March 2026 |chapter=Coastal, Heath and Wetland Vegetation}}</ref>
== References == {{Reflist}}
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pallida