Panarctic Flora

800308b Veronica serpyllifolia subsp. humifusa (Dicks.) Syme

• Syme in Sowerby, Engl. Bot., ed. 3B, 6: 158 (1866). - Veronica humifusa Dicks., Trans. Linn. Soc. London 2: 288 (1794). Type: Scotland, 1792, leg. J. Dickson. - Veronicastrum serpyllifolium subsp. humifusum (Dicks.) W.A. Weber, Phytologia 62: 437 (1987).
• Veronica tenella All., Fl. Pedem. 1: 75 (1785). Described from the southwestern Alps (Italy).
• Veronica serpyllifolia var. borealis Laest., Nova Acta Regiae Soc. Sci. Upsal. 11: 211 (1839). Described from northern Scandinavia. - Veronica borealis (Laest.) Neuman, Sver. Fl.: 132 (1901).

2n= 14 16 (2x). - Europe, Far East, U.S.A. (W). - Several reports.

Geography: North American (NE) & European (N/C) & Asian (C) - amphi-Pacific - Cordilleran & South American?: ALA CAN.

Notes: Veronica serpyllifolia subsp. humifusa does not have the explainable geographical range expected of a taxon. It is found widely dispersed in coastal, northern, and mountainous areas in the Northern Hemisphere, perhaps except for northern Russia-Siberia. In addition, it is reported from some isolated islands (the subtropical Azores are mentioned by Hultén and Fries 1986) and probably South America. All the three epithets applied to it are based on European plants: from the British Isles (Dickson's "humifusa"), the southwestern Alps (Allioni's "tenella"), and northern Scandinavia (Laestadius' "borealis"). Hylander (1945) stated that: "Dagegen liegen von da in the southwestern Alps, Allioni's ["tenella"] zahlreichen Ex. vor, die man von die nordischen Pflanze unmöglich unterscheiden kann - nach Williams, der italienische Ex. mit den Originalex. Dicksons aus Schottland Dickson's ["humifusa"] verglich, stimmten die ersteren mit den letztgenannten "Haar für Haar" überein ... Allionis Figur könnte ebenso gut nach einem schwedischen Ex. gezeichnet sein", i.e., Hylander found full morphological identity, "hair by hair", among "tenella", "borealis", and "humifusa".

Subspecies humifusa is generally characterized by being more low-grown than subsp. serpyllifolia, with efficiently rooting branches forming carpets, shorter racemes also in fruiting stage, a dark brownish pubescence, presence of dark glandular hairs in the inflorescence vs. eglandular in subsp. serpyllifolia, pedicels longer than the calyx, flowers slightly larger, petals sky blue vs. very pale blue to white with bluish stripes in subsp. serpyllifolia, and capsule with a cuneate base vs. rounded. These characters for subsp. humifusa fit at least the plants in northern Fennoscandia and Alaska. The differences are many and in different parts of the plant. They cannot readily be explained away as a recurrent mutation. Together with the general sympatry, they indicate that rank as a species would be more appropriate than as a race. However, in Fennoscandia the two taxa are distributed like eco-geographical races. Subspecies serpyllifolia is partly weedy and occurs throughout the region except for the northern boreal woodlands and mountains. Subspecies humifusa is a specialist of just these boreal forest swamps, swampy willow thickets, river banks, cold springs, and snowbank environments in mountainous areas. It therefore mainly occurs apart from subsp. serpyllifolia. Where they meet, mainly because subsp. serpyllifolia has been introduced along paths or roads, obvious intermediates (probably fertile) occur in sites with intermediate conditions.

Until more evidence is available, "humifusa" is entered for the Checklist as subspecies. Its rank has varied in more recent decades from species to variety. As to name, this is a distinctly northeastern continental and boreal taxon in Fennoscandia and someone should check again the British type of "humifusa". The combinations utilizing Laestadius' northern Fennoscandian name "borealis" might be the most appropriate for arctic plants if any differences are found.