Hybrids In Natural Populations Research Articles

GENOMIC COADAPTATION AND DEVELOPMENTAL STABILITY WITHIN INTROGRESSED POPULATIONS OF ENNEACANTHUS GLORIOSUS AND E. OBESUS (PISCES, CENTRARCHIDAE).

Using fluctuating bilateral asymmetry as a measure of developmental stability, we tested the hypothesis that genomic coadaptation mediates developmental stability in natural populations. Hybrid populations were more asymmetrical than populations of the parental species, and ranks of overall developmental instability were positively correlated with ranks of mean heterozygosity in these populations. The failure to find increased asymmetry in previous studies of natural hybrid populations (Jackson, 1973a, 1973b; Felley, 1980) suggests that such populations may have re-evolved coadapted genomes. Increased asymmetry in hybrid Enneacanthus populations may reflect the youthfulness of these populations.

Character Coherence in Natural Hybrid Populations in Plants

Natural hybrid populations in Opuntia, Iris, Aquilegia, Gilia, and Oxytropis are examined or reexamined for character coherence. Coherence is present in some but not in other populations. The differences between plant groups and between populations are greater than expected, according to the standard theory. A reassessment of the standard theory reveals three flaws leading to overestimates of the amount of coherence: (1) failure to exclude parental-type individuals from hybrid population samples, (2) use of non-quantitative pictorialized scatter diagrams rather than correlation coefficients, and (3) the assumption that selection will always favor the parental types in natural hybrid populations. An alternative framework recognizing more variable factors is proposed. Population-to-population differences in character coherence in natural hybrid populations can be accounted for with this alternate approach.

Use of partial löwdin (PLA) and limited expansion of diatomic overlap (LEDO) integral approximation methods in molecular orbital calculations of the isomer pairs HCN, CNH and FCN, CNF

Molecular orbital calculations, using a free atom double zeta basis set and embodying the PLA and LEDO integral approximation methods, are performed on the isomer pairs HCN, CNH and FCN, CNF in their respective linear configurations. For each integral approximation method, the C—N separation is fixed at the experimental value for FCN and, for variable X—C and X—N separations, the calculated total energies, orbital energies, one-electron density functions and natural hybrid populations are compared for each pair of isomers. One ab initio calculation is also performed for each isomer at a selected molecular geometry. Additional calculations are performed on the related model ionic systems H+CN– and CN–H+ to provide further insight into the bonding in the two hydrocyano species.

Flavonoid Analysis of Hybridization in Rhododendron Section Pentanthera (Ericaceae)

Flavonoid Analysis of Hybridization in Rhododendron Section Pentanthera (Ericaceae)

Significance of the blood protein pattern in the identification of Bufo calamita Laur., Bufo viridis Laur. and their hybrids (Amphibia, Anura, Bufonidae)

Electrophoretic investigations of the serum protein patterns of natterjacks (Bufo calamita Laur.) from the Iberian Peninsula and from Western and Central Europe, and of green toads (Bufo viridis Laur.) from Central Europa, Asia Minor and North Africa show that the two species differ disctinctly in the position of their albumin fractions. The identification of problematic specimens can result from the production of mixed serum with specimens of both species. As the albumin fraction of hybrids is doubled according to this method, it is also suitable for demonstrating the existence of such hybrids in natural populations.

HYBRIDS BETWEEN LOLIUM PERENNE L. AND FESTUCA PRATENSIS HUDS. I. CROSSING AND INCOMPATIBILITY

SUMMARYNatural hybrids between Lolium perenne and Festuca pratensis occur in old grassland; diploids and two types of triploids, festucoid and loloid, may occur. Attempts were made to produce similar hybrids experimentally, both by crossing in the glasshouse, and in mixed plots in the field. It was found very difficult to produce F1 hybrids, except for the production of festucoid triploids by crossing diploid Lolium with tetraploid Festuca. No triploids were obtained from diploid‐diploid crosses, but there was evidence of unreduced gametes in the appearance of tetraploid progeny from diploid–tetraploid crosses within Lolium perenne.The hybrids were found to be nearly sterile, but attempts to backcross in the glasshouse yielded a few progeny, both from diploids and triploids. Lolium was a much more successful pollen parent than Festuca. The progeny from diploids were mostly diploid, but included a few triploids and aneuploids. Triploid hybrids produced a wide range of progeny, varying from fourteen to twenty‐eight chromosomes.The difficulty of crossing, and reciprocal differences in compatibility which occur are apparently due to seed incompatibility, probably controlled by the relationship between the genomes and the plasmon in the endosperm.It is concluded that the abundance of hybrids in natural populations must be explained ecologically.

Interspecific hybridization between diploid species of Lotus (Leguminosae)

An interspecific hybridization study has been carried out between seven diploid species of Lotus (L. alpinus Schleich., L. japonicus (Regel) Larsen, L. filicaulis Dur., L. schoelleri Schweinf., L. krylovii Schischk. and Serg., L. tenuis Waldst. et Kit., and L. corniculatus var. minor Baker) closely related to L. corniculatus L. A total of 139 interspecific hybrids were produced in 16 combinations of the 7 species. Nine of these crosses were produced for the first time and four were obtained by means of embryo-culture. The growth habit, number of florets per umbel, flower color expression, HCN reaction and 15 metrical traits were compared between parents and hybrids. The relative case with which some hybrids were produced suggested that during the early evolutionary history of the genus species diversification could have originated through interspecific hybridization and subsequent gene differentiation. In some crosses, the hybrids resembled one parent more closely than the other. This close morphological affinity between the hybrids and one of their parents would make it extremely difficult to detect such hybrids in natural populations and probably aceounts for the prevailing belief that there is little or no hybridization in nature.

ON THE NATURAL HYBRID POPULATION OF HEMEROCALLIS

A large natural hybrid population between Hemerocallis middendorffii and Hemerocallis yezoensis occurs at Otanoshike and its neighborhood in the eastern part of Hokkaido, Japan. This report is the result of a comparative study on external morphology and cytological analysis of the hybrid swarm at Otanoshike and of the parental species from various localities in Hokkaido. The hybrid population at Otanoshike represents morphologically an "introgressive status", and this fact is well understood in connection with the ecological condition of the habitat. Among the hybrid swarm intermediate types are dominant. Cytologically, all the material examined was diploid, i.e., it had 2n = 22.