Craticula johnstoniae Bahls, 2013

Bahls, Loren, 2013, New diatoms (Bacillariophyta) from western North America, Phytotaxa 82 (1), pp. 7-28 : 22-23

Craticula johnstoniae Bahls , sp. nov. ( Figs 90–95 )

Valves lanceolate with rostrate to subcapitate apices. Valve length 78–105 µm; valve width 18.0– 19.3 µm. Axial area narrow, flaring somewhat to merge with an elliptic and slightly wider central area. Raphe filiform and somewhat sinuous with inflated and relatively distant proximal ends that are bent to the same side. Striae parallel in the middle, becoming weakly radiate and then convergent near the apices, 14 in 10 µm at valve center, 17 in 10 µm at the apices. One or more striae in the central area slightly shorter than adjacent striae. Areolae 28 in 10 µm. “Heribaudii” valves present with more strongly radiate striae and lower stria density; craticula valves not observed.

Holotype: — CANADA, Alberta: Waterton Lakes National Park, Akamina Pools , 49.0314 o N, 114.0428 o W, elev. 1646 m, coll. B. Johnston, 7 July 2009. MDC sample 456101; holotype slide MDC 124-19 ( Figs 90–93 ) (circled holotype specimen in Fig. 90 ). MONTU!

Isotypes: —MDC slide 40-44 (MONTU!); ANSP GC 65109.

Paratypes: — CANADA, Alberta: Waterton Lakes National Park, Indian Springs Pond , 49.1297 o N, 113.8731 o W, elev. 1372 m, coll. B. Johnston, 5 June 2009. MDC sample 454301; MDC slides 40-26, 124-1 ( Fig. 95 ). MONTU !— USA, Montana: Jefferson County, Pond near Park Lake , 46.4417 o N, 112.1731 o W, elev. 2,000 m, coll. L. Bahls, 30 May 2012. MDC sample 492101; MDC slides 41-17 ( Fig. 94 ), 126-11. MONTU !

Etymology:—This species is named for Barb Johnston, the Parks Canada biologist who collected the holotype sample and one of the paratype samples.

Observations:—“Heribaudii“ valves ( Fig. 91 ) have more strongly radiate striae and lower stria density. The rostrate to subcapitate apices of C. johnstoniae distinguish this taxon from C. acidoclinata Lange- Bertalot & Metzeltin (1996: 41), in which the apices are never or only slightly protracted. Craticula cuspidata (Kützing) D.G. Mann in Round et al. (1990: 666) has rhombic-lanceolate valves with very narrow apices and a central area with concave sides. Craticula sardiniana sp. nov. (this paper, Figs 96–101 ) has wider, unprotracted apices.

Distribution and Ecology: — Craticula johnstoniae evidently tolerates a wide range of water quality conditions. One habitat, a pond in Jefferson County, Montana is circumneutral (pH 6.98) with low specific conductance (46 µS/cm). Another, Indian Springs Pond in Waterton Lakes National Park, is alkaline (pH 8.1) with moderate specific conductance (313 µS/cm). At these locations Craticula johnstoniae was found in association with C. acidoclinata , C. cuspidata , and C. sardiniana .

Figures

FIGURES 90–101: Craticula johnstoniae, Craticula sardiniana. Figs 90–95: Craticula johnstoniae. Figs 90–93: Akamina Pools, Waterton Lakes National Park, Alberta (type locality). Fig. 90: Holotype specimen. Fig. 91: “Heribaudii“ valve. Fig. 94: Pond near Park Lake, Jefferson County, Montana. Fig. 95: Indian Springs Pond, Waterton Lakes National Park, Alberta. Figs 96–101: Craticula sardiniana. Figs 96, 98: Indian Springs Pond, Waterton Lakes National Park, Alberta (type locality). Fig. 96: Holotype specimen. Figs 97, 99–101: Skinner Pond No. 1, Beaverhead County, Montana. Scale bars: 10 µm.