Research Article Comparing covariance matrices: random skewers method compared to the common principal components model

Comparisons of covariance patterns are becoming more common as interest in the evolution of relationships between traits and in the evolutionary phenotypic diversification of clades have grown. We present parallel analyses of covariance matrix similarity for cranial traits in 14 New World Monkey genera using the Random Skewers (RS), T-statistics, and Common Principal Components (CPC) approaches. We find that the CPC approach is very powerful in that with adequate sample sizes, it can be used to detect significant differences in matrix structure, even between matrices that are virtually identical in their evolutionary properties, as indicated by the RS results. We suggest that in many instances the assumption that population covariance matrices are identical be rejected out of hand. The more interesting and relevant question is, How similar are two covariance matrices with respect to their predicted evolutionary responses? This issue is addressed by the random skewers method described here

The comparative efficiency of a brown algal-derived biostimulant extract (AMPEP), with and without supplemented PGRs: the induction of direct, axis shoots as applied to the propagation of vegetative seedlings for the successful mass cultivation of three commercial strains of Kappaphycus in Sabah, Malaysia

Three strains of Kappaphycus spp. (viz. K. alvarezii tambalang brown and green and K. striatus sacol green) were used in the present study to optimize the use of Ascophyllum (Acadian) marine plant extract powder (AMPEP) as a culture medium ingredient acting as a biostimulant, applied with, and without, the addition of terrestrial plant growth regulators (PGRs). This was undertaken in order to develop management tools and best practice recommendations for the mass production of new plantlets (seedlings) for industrial, nursery, and out-planting purposes in eastern Malaysia, Sabah, and Peninsular Malaysia (i.e., Langkawi, Kedah and Batu Maung, Penang). After 45 days of laboratory incubation, the three strains tested demonstrated their best performances at 3 mg L−1 of AMPEP, supplemented with PGR. This evaluation was based on the longest direct axes formed, the shortest time to their appearance, and also their highest percentage emergence. Kappaphycus alvarezii (tambalang green) had the longest direct axes (7.0 ± 0.23 mm), followed by K. alvarezii (tambalang brown) at (6.4 ± 0.48 mm) and finally K. striatus (sacol green). In terms of the highest percentage of direct axes formed, K. alvarezii (tambalang brown), K. alvarezii (tambalang green), and K. striatus (sacol green) were recorded as follows: 100 ± 0.00, 99 ± 1.34, and 98 ± 2.66, respectively. The shortest duration taken for the emergence of direct axes was observed in K. alvarezii (tambalang green) followed by tambalang brown and K. striatus (sacol green) on days 9, 10, and 15, respectively. The use of a brown seaweed-derived extract acting as a biostimulant and as the main ingredient of the culture medium for the micropropagation of three strains of Kappaphycus was highly encouraging and one which may be promoted as a protocol for the economic and commercial mass production of new plantlets (asexual seedlings) which are an urgent requirement for Malaysian seaweed farming to meet its full potential