Abstract
Phylogenetic analysis has revealed that Argyranthemum broussonetii is polyphyletic, with subsp. broussonetii (Tenerife) and subsp. gomerensis (La Gomera) resolved in separate clades within the Macaronesian endemic genus Argyranthemum. We show that A. broussonetii subsp. broussonetii and subsp. gomerensis are similar in leaf traits, likely a consequence of adaptation to similar habitats, but that the two can readily be distinguished based on capitula and cypselae characteristics. Indeed, A. broussonetii subsp. gomerensis was found to share greater affinity with A. callichrysum, also from La Gomera based on capitula and cypselae characters, in agreement with its phylogenetic placement. Therefore, we propose that A. broussonetii subsp. gomerensis should be recognized as a subspecies of A. callichrysum, specifically A. callichrysum subsp. gomerensis. A key to differentiate A. broussonetii, A. callichrysum subsp. callichrysum and subsp. gomerensis is provided.Citation: White O. W., Reyes-Betancort J. A., Chapman M. A. & Carine M. A. 2021: Recircumscription of the Canary Island endemics Argyranthemum broussonetii and A. callichrysum (Asteraceae: Anthemideae) based on evolutionary relationships and morphology. – Willdenowia 51: 129–139.Version of record first published online on 29 April 2021 ahead of inclusion in April 2021 issue.
Highlights
Argyranthemum Webb is the largest endemic flowering plant genus of the Macaronesian region
We propose that A. broussonetii subsp. gomerensis should be recognized as a subspecies of A. callichrysum, A. callichrysum subsp. gomerensis
We found that Argy ranthemum broussonetii subsp. broussonetii and subsp. gomerensis are similar in leaf traits including primary lobe length and leaf dissection, which supports their current taxonomic treatment
Summary
Argyranthemum Webb is the largest endemic flowering plant genus of the Macaronesian region It comprises 24 species (39 terminal taxa when subspecies are considered; Humphries 1976) and is distributed across the archipelagos of Madeira, the Selvagens and the Canary Islands. Argyranthemum broussonetii (Pers.) Humphries is endemic to the Canary Islands where it is restricted to laurel forest clearings on Tenerife and La Gomera. It is distinguished from other members of the genus by its large bipinnatifid leaves, its often wingless ray cypselae, typically two-winged disc cypselae, and large capitula and ray florets. Gomerensis Humphries endemic to La Gomera (Fig. 1; Fig. 2) He differentiated the two largely by size, with subsp. He differentiated the two largely by size, with subsp. broussonetii larger than subsp. gomerensis in stature, leaf size, involucre width and ray cypselae dimensions
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