Distribution, morphology and ecological niche of Batrachospermum and Sheathia species (Batrachospermales, Rhodophyta) in the fontanili of the Po plain (northern Italy)

Figures & data

Fig. 1. Study area with the location of the lowland springs (fontanili) sampled (1: Averolda, 2: Becchilsù, 3: Belprato, 4: Boscovito, 5: Ca Nova, 6: Calcio, 7: Cavetti, 8: Chigaluzza, 9: Cna Volpe, 10: Crocetta, 11: Est Pompiano, 12: Fascina, 13: Isso Grande, 14: Isso Piccolo, 15: Lametta, 16: Mirandola, 17: Negroni, 18: Palazzina, 19: Pellegrina, 20: Pratizagni, 21: Saragozza, 22: Serafina, 23: Zemia). For more detailed location data see Supplementary Table 1. All fontanili were between 40° 23′−40° 30′ longitude and 9° 43′−10° 0′ latitude.

Figs 2–14. Batrachospermum gelatinosum. Fig. 2. Whorls with carposporophytes. Figs 3–5. Lanceolate, sessile trichogynes with more or less elongated end and more or less swollen central part (marked Ge.(sk) in the text) from specimens collected at springs Pellegrina (Fig. 3), Isso Piccolo (Fig. 4), and Crocetta (sequenced specimen, Fig. 5). Figs 6, 7. Deformed trichogynes with long basal stalk or just a hinted knob (marked Ges(k) in the text) from a specimen collected at Cna Volpe, the spring with the best environmental conditions among the 23 investigated. Figs 8–10. Deformed trichogynes with more or less long stalk and knobs (marked Ge.sk in the text) from specimens collected in three springs with the poorest environmental conditions [Pratizagni (Fig. 8), Saragozza (Fig. 9), Fascina (Fig. 10)]. Fig. 11. Three carpogonia on the same fascicle branch from the sequenced specimen collected at the spring Averolda. Note the basal knob (arrow) on trichogyne of the central carpogonium (arrow). Fig. 12. Two carpogonia on the same fascicle branch from the sequenced specimen collected at the spring Est Pompiano, the one on the left with stalk and knob (arrow). Figs 13, 14. B. gelatinosum f. spermatoinvolucrum. Specimen sequenced with spermatangia on the top of involucral filaments (arrowheads). Fig. 2, scale bar = 50 µm; Figs 3–14, scale bar = 20 µm.

Table 1. Physical-chemical parameters for fontanili in which species of Batrachospermum and Sheathia occurred.

			S. boryana	S. arcuata	B. atrum	B. gelatinosum
						SP	Ge.sk	Ge.s(k) & Ge.(sk)
T	°C	r	14.6–14.9	13.8–15.0	13.8	15.0	13.5–16.4	13.7–15.4
		m±sd					14.6±0.7	14.3±0.7
pH		r	7.2–7.3	6.7–7.2	7.0	7.0	6.9–7.3	6.9–7.2
		m±sd					7.0±0.1	7.0±0.1
Cond	μS cm^–1	r	487–597	636–715	825	620	487–819	525–825
		m±sd					694±93	696±123
DO	%	r	54.2–58.0	18.3–42.7	20.3	24.1	3.0–58.0	3.0–55.3
		m±sd					30.3±16.2	25.8±17.8
DIC	mM	r	4.3–6.5	6.7–7.2	7.7	6.2	4.3–8.0	4.5–8.0
		m±sd					6.8±1.1	6.8±1.8
NH4^+	μg l^–1	r	10–60	0–10	10	10	0–30	0–60
		m±sd					10±10	10±20
NO2^–	μg l^–1	r	4	1–5	15	1	1–15	1–15
		m±sd					4±4	8±6
NO3^–	mg l^–1	r	20.4–27.6	37.0–43.4	23.2	37.3	20.4–53.6	19.1–47.8
		m±sd					38.8±9.5	30.9±8.9
PO4^3–	μg l^–1	r	3–5	4–11	1	4	1–4	1–5
		m±sd					3±1	3±1
SiO2	mg l^–1	r	3.3–4.9	2.7–2.9	3.7	2.7	2.2–4.9	2.6–4.8
		m±sd					3.4±0.8	3.7±0.8

Minimum–maximum = r, mean±st.dev = m±sd. Data for B. gelatinosum are split in: SP = B. gelatinosum f. spermatoinvolucrum; Ge.sk = specimens with more than 30% trichogynes deformed by knobs and stalks Ge.(sk) = specimens with fewer than 30% trichogynes deformed by knobs and stalks; Ge.s(k) = specimens with more than 30% trichogynes deformed almost exclusively by long stalks. Abbreviations of physical-chemical parameters: T = temperature; Cond = Conductivity, DO = dissolved oxygen %, DIC = dissolved inorganic carbon, NH₄⁺ = ammonia, NO₂^– = nitrite, NO₃^– = nitrate, PO₄^3– = soluble reactive phosphorus, SiO₂ = reactive silica.

Fig. 15. Biplot of the first two axes from the niche analysis. AR = Sheathia arcuata; BO = S. boryana; ATR = Batrachospermum atrum; SP = B. gelatinosum f. spermatoinvolucrum; Ge.sk = specimens of B. gelatinosum with more than 30% trichogynes deformed by knobs and stalks Ge.(sk) = specimens of B. gelatinosum with fewer than 30% trichogynes deformed by knobs and stalks; Ge.s(k) = specimens of B. gelatinosum with more than 30% trichogynes deformed almost exclusively by long stalks.

Fig. 16. Scatter plot on the first factorial plan from the niche analysis of species and springs. AR = Sheathia arcuata; BO = S. boryana; ATR = Batrachospermum atrum; SP = B. gelatinosum f. spermatoinvolucrum; Ge.sk = specimens of B. gelatinosum with more than 30% trichogynes deformed by knobs and stalks; Ge.(sk) = specimens of B. gelatinosum with fewer than 30% trichogynes deformed by knobs and stalks; Ge.s(k) = specimens of B. gelatinosum with more than 30% trichogynes deformed almost exclusively by long stalks.

Table 2. Results of the Poisson regression for Batrachospermum gelatinosum groups and fontanili environmental variables.

Ge.sk	Estimate	Std. Error	P
	AIC=46.285, Null Deviance=36.048, Residual Deviance=15.231
(Intercept)	149.792	82.967	0.071
T	−0.051	1.798	0.978
pH	−18.422	8.251	0.026
SiO2	0.579	0.830	0.485
DO	−1.197	0.779	0.124
DIC	−3.299	1.989	0.097
NO2^−	8.710	4.448	0.050
NH4^+	2.169	1.148	0.059
NO3^−	0.002	0.004	0.614
Ge.(sk)	AIC=41.056, Null Deviance=36.048, Residual Deviance=14.461
(Intercept)	142.863	50.596	0.005
pH	−17.901	6.436	0.005
DO	−0.903	0.532	0.090
DIC	−2.530	0.998	0.011
NO2^−	7.737	3.008	0.010
NH4^+	1.790	0.720	0.013
Ge.s(k)	AIC=30.089, Null Deviance=24.956, Residual Deviance=14.483
(Intercept)	54.6928	25.0635	0.0291
T	−3.5152	1.5798	0.0261
DIC	−1.1037	0.6545	0.0918
NO2^–	8.1114	4.2913	0.0587

Ge.sk = specimens with more than 30% trichogynes deformed by knobs and stalks; Ge.(sk) = specimens with fewer than 30% trichogynes deformed by knobs and stalks; Ge.s(k) = specimens with more than 30% trichogynes deformed almost exclusively by long stalks. T = temperature; Cond = Conductivity, DO = dissolved oxygen, DIC = dissolved inorganic carbon, NH₄⁺ = ammonia, NO₂^– = nitrite, NO₃^– = nitrate, SiO₂ = reactive silica