Developmental plasticity and genotype–environment interactions influence valve morphology in the Cyclotella meneghiniana species complex (Bacillariophyceae)

Figures & data

Fig. 1. Phylogenetic tree of Cyclotella species and the strains used to investigate developmental plasticity based on Bayesian analysis (TN + G) of partial 28S rDNA sequences (D1/D2 regions). The numbers at the nodes are posterior probabilities (PP) above 0.50. DNA sequences determined in this study are in bold. Scale bar represents 3 substitutions per 100 nucleotides.

Table 1. Strain characteristics.

Strain designation	Date of sampling	Location	Salinity of sampling point (psu)
SR-0	10.7.2006	A freshwater pond in Musashi kyuryo National Government Park (36°5′40″N, 139°22′27″E)	0
MG-0	1.7.2006	5.3 km from the river mouth of the Meguro River (35°38′28″N, 139°42′10″E)	1
HK	15.10.2006	12.1 km from river mouth of the Ara River (35°44′38″N, 139°49′9″E)	4
SR-1		F1 of sexual reproduction within SR-0	–
SR-2		F1 of sexual reproduction within SR-0	–
SR-3		F1 of sexual reproduction within SR-0	–
MG-1		F1 of sexual reproduction within MG-0	–

Fig. 2. Variables in the morphological analyses, illustrated on a C. meneghiniana valve. A, number of CFP (central fultoportulae); B, number of striae; C, valve diameter; and D, diameter of the central area.

Table 2. Collection sites and water quality data.

Collection site	Location	Distance from the river mouth (km)	Salinity (psu)	pH	Water temperature (°C)
A	(35°47′15″N, 139°43′52″E)	22.3	0	7.9	19
B	(35°44′38″N, 139°49′9″E)	12.1	4	7.6	22
C	(35°42′49″N, 139°50′60″E)	7.6	4	7.5	16
D	(35°38′41″N, 139°50′59″E)	0	15	7.5	16

Fig. 3. Morphological traits of seven clonal strains of C. meneghiniana in freshwater medium (FW: salinity 0) and 50% seawater medium (SW: salinity 17 psu). Reaction norms are shown for (a) the number of central fultoportulae (CFP), (b) the number of striae, (c) the diameter of the central area, and (d) the valve diameter. Bars indicate mean ± standard error (SE).

Table 3. The results of GLM summarizing the effect of salinity and strain on the traits of C. meneghiniana; d.f. = degrees of freedom.

Trait	Source	d.f.	F	P
Number of CSP	Strain (G)	6	77.88	<0.001
	Salinity (E)	1	129.97	<0.001
	G × E	6	2.13	0.046
Number of striae	Strain (G)	6	4499.91	<0.001
	Salinity (E)	1	248.09	<0.001
	G × E	6	42.40	<0.001
Diameter of central area	Strain (G)	6	10261.87	0.032
	Salinity (E)	1	4.59	<0.001
	G × E	6	31.05	<0.001
Diameter	Strain (G)	6	24052.00	0.001
	Salinity (E)	1	10.76	<0.001
	G × E	6	5.22	<0.001

Table 4. Pairwise comparison of the effect of salinity in each strain. ‘Increase’ and ‘decrease’ tabulate significant changes (P < 0.05) in seawater vs. freshwater; n.s. = not significant.

Trait	Increase	Decrease	n.s.
Number of CSP	All strains	–	–
Number of striae	SR-0, SR-1, SR-3, HK	SR-2	MG-0, MG-1
Diameter of central area	SR-0, SR-1, SR-3, HK	SR-2, MG-1	MG-0
Diameter	SR-1	SR-0, HK	SR-2, SR-3, MG-0, MG-1

Table 5. Pairwise comparison of G × E interactions (SR-0, MG-0 and HK).

Combination of strain	Trait	P (adjusted)
SR-0 × MG-0	Number of CSP	0.086
	Number of striae	<0.001
	Diameter of central area	<0.001
	Diameter	0.175
SR-0 × HK	Number of CSP	1
	Number of striae	0.037
	Diameter of central area	0.544
	Diameter	0.643
MG-0 × HK	Number of CSP	0.138
	Number of striae	<0.001
	Diameter of central area	<0.001
	Diameter	0.312

Fig. 4. Morphological traits of specimens at each collection site (A, B, C and D). (a) Number of central fultoportulae (CFP), (b) number of striae, (c) diameter of the central area, (d) valve diameter. Bars indicate mean ± standard error (SE).

Table 6. The effect of collection site and valve diameter on C. meneghiniana traits. For ‘significant pairs’ the level of significance used was P = 0.05

Trait	Source	d.f	F	P	Significant pairs
Number of CSP
	Collection site	3	4.96	0.002	AD, BD, CD
	Diameter	1	34.16	<0.001	AB, AC, AD, BD, CD
	Collection site × diameter	3	1.80	0.145	–
Number of striae
	Collection site	3	50.94	<0.001	AD, BD, CD
	Diameter	1	769.21	<0.001	All pair combinations
	Collection site × diameter	3	10.54	<0.001	AB, AD, BD, CD
Diameter of central area
	Collection site	3	49.34	<0.001	AD, BD, CD
	Diameter	1	808.00	<0.001	All pair combinations
	Collection site × diameter	3	17.44	<0.001	AB, AC, AD, BD, CD
Diameter
	Collection site	3	7.89	<0.001	AD, BD, CD