Pachycladon exile is a species of plant in family Brassicaceae that is endemic to the South Island of New Zealand. Commonly known as limestone cress, it is a perennial herb with hairy leaves that is only found on one specific limestone outcrop site. It has been used to analyse principles behind adaptive radiation, together with other species of Pachycladon. Its conservation status is Threatened - Nationally Critical.
| Pachycladon exile | |
|---|---|
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| Herbarium specimen of Pachycladon exile | |
Scientific classification 
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| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Brassicales |
| Family: | Brassicaceae |
| Genus: | Pachycladon |
| Species: | P. exile
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| Binomial name | |
| Pachycladon exile (Heenan) Heenan & A.D.Mitch.
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| Synonyms | |
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Ischnocarpus exilis Heenan | |
Taxonomy
editPachycladon exile is a species of plant that is endemic to the South Island of New Zealand in the family Brassicaceae.[1][2] P. exile was originally described in 1999 as Ischnocarpus exilis by Peter Heenan.[3] It was later transferred to the genus Pachycladon in 2002.[4]
P. exile is morphologically similar to P. novae-zelandiae. It can be distinguished from that species by its slender growth habit, terete ovary, slender siliques, smaller flowers, leaves and inflorescences, and a style that is small but distinct.[3] It is also similar to P. cheesemanii, as both species are polycarpic and have woody caudices, short branches, slender inflorescences, terete siliques, heterophyllous leaves, and seeds that are uniseriate and without wings.[5][6]
Description
editP. exile is a perennial, polycarpic, heterophyllous rosette plant that has slender inflorescences, a woody caudex, short branches, and hairy, heterophyllous leaves.[1][3][6] Its fruit is a terete silique, and its seeds do not have wings, and are uniseriate.[6][3]
Distribution and habitat
editPachycladon exile is only found on a specific limestone outcrop site in the Waitaki Valley.[7] It is found in habitats that have a high fertility rock substrate, such as limestone, schist, and volcanics, from 10 to 1600 m above sea level.[8]
Phylogeny
editP. exile is closely related to P. cheesemanii.[6][9] Alongside other Pachycladon species it has been used to analyse principles behind adaptive radiation.[10]
Conservation status
editPachycladon exile is listed as Threatened - Nationally Critical, with the qualifiers CD (Conservation Dependent), DPT (Data Poor Trend), EF (Extreme Fluctuations), OL (One Location) in the most recent assessment (2023) of the New Zealand Threatened Classification for plants.[11]
It is the sixth most endangered species in New Zealand.[7]
It was featured as Critter of the Week on 12 May 2019 on Radio New Zealand.[7]
References
edit- ^ a b Sooda, A.; Song, J.; Jameson, P. E.; Clemens, J. (2011). "Phase change and flowering in Pachycladon exile and isolation of LEAFY and TERMINAL FLOWER1 homologues". New Zealand Journal of Botany. 49 (2): 281–293. Bibcode:2011NZJB...49..281S. doi:10.1080/0028825X.2010.548070.
- ^ "Pachycladon exile". New Zealand Plant Conservation Network. Retrieved 2024-10-19.
- ^ a b c d Molloy, B. P. J.; Edgar, E.; Heenan, P. B.; De Lange, P. J. (1999). "New species of Poa (Gramineae) and Ischnocarpus (Brassicaceae) from limestone, North Otago, South Island, New Zealand". New Zealand Journal of Botany. 37 (1): 41–50. Bibcode:1999NZJB...37...41M. doi:10.1080/0028825X.1999.9512610.
- ^ Heenan, P. B.; Mitchell, A. D.; Koch, M. (2002). "Molecular systematics of the New Zealand Pachycladon (Brassicaceae) complex: Generic circumscription and relationships to Arabidopsis sens. lat. and Arabis sens. lat". New Zealand Journal of Botany. 40 (4): 543–562. Bibcode:2002NZJB...40..543H. doi:10.1080/0028825X.2002.9512815.
- ^ Heenan, P. B. (2009). "A new species of Pachycladon (Brassicaceae) from limestone in eastern Marlborough, New Zealand". New Zealand Journal of Botany. 47 (2): 155–161. Bibcode:2009NZJB...47..155H. doi:10.1080/00288250909509803.
- ^ a b c d Yogeeswaran, Krithika; Voelckel, Claudia; Joly, Simon; Heenan, Peter B. (2011). "Pachycladon". Wild Crop Relatives: Genomic and Breeding Resources. pp. 227–249. doi:10.1007/978-3-642-14871-2_14. ISBN 978-3-642-14870-5.
- ^ a b c "Critter of the Week Limestone Cress". RNZ. 2019-05-10. Retrieved 2024-07-30.
- ^ Mandáková, Terezie; Heenan, Peter B.; Lysak, Martin A. (2010). "Island species radiation and karyotypic stasis in Pachycladon allopolyploids". BMC Evolutionary Biology. 10 (1): 367. Bibcode:2010BMCEE..10..367M. doi:10.1186/1471-2148-10-367. PMC 3014931. PMID 21114825.
- ^ McBreen, K.; Heenan, P. B. (2006). "Phylogenetic relationships of Pachycladon (Brassicaceae) species based on three nuclear and two chloroplast DNA markers". New Zealand Journal of Botany. 44 (4): 377–386. Bibcode:2006NZJB...44..377M. doi:10.1080/0028825X.2006.9513029.
- ^ Joly, Simon; Heenan, Peter B.; Lockhart, Peter J. (2014). "Species Radiation by Niche Shifts in New Zealand's Rockcresses (Pachycladon, Brassicaceae)". Systematic Biology. 63 (2): 192–202. doi:10.1093/sysbio/syt104. PMID 24335427.
- ^ de Lange, Peter J.; Gosden, Jane; Courtney, Shannel P.; Fergus, Alexander J.; Barkla, John W.; Beadel, Sarah M.; Champion, Paul D.; Hindmarsh-Walls, Rowan; Makan, Troy; Michel, Pascale (October 2024). "Conservation status of vascular plants in Aotearoa New Zealand, 2023" (PDF). New Zealand Threat Classification Series. 43: 1–105.