Small genomes and large seeds: chromosome numbers, genome size and seed mass in diploidAesculusspecies (Sapindaceae)

Abstract

Background and Aims Aesculus L. (horse chestnut, buckeye) is a genus of 12-19 extant woody species native to the temperate Northern Hemisphere. This genus is known for unusually large seeds among angiosperms. While chromosome counts are available for many Aesculus species, only one has had its genome size measured. The aim of this study is to provide more genome size data and analyse the relationship between genome size and seed mass in this genus. Methods Chromosome numbers in root tip cuttings were confirmed for four species and reported for the first time for three additional species. Flow cytometric measurements of 2C nuclear DNA values were conducted on eight species, and mean seed mass values were estimated for the same taxa. Key Results The same chromosome number, 2n ¼ 40, was determined in all investigated taxa. Original measurements of 2C values for seven Aesculus species (eight taxa), added to just one reliable datum for A. hippocastanum, confirmed the notion that the genome size in this genus with relatively large seeds is surprisingly low, ranging from 0Á955 pg 2C-1 in A. parviflora to 1Á275 pg 2C-1 in A. glabra var. glabra. Conclusions The chromosome number of 2n ¼ 40 seems to be conclusively the universal 2n number for nonhybrid species in this genus. Aesculus genome sizes are relatively small, not only within its own family, Sapindaceae, but also within woody angiosperms. The genome sizes seem to be distinct and non-overlapping among the four major Aesculus clades. These results provide an extra support for the most recent reconstruction of Aesculus phylogeny. The correlation between the 2C values and seed masses in examined Aesculus species is slightly negative and not significant. However, when the four major clades are treated separately, there is consistent positive association between larger genome size and larger seed mass within individual lineages.

Cytotype variation, cryptic diversity and hybridization in Ranunculus sect. Batrachium revealed by flow cytometry and chromosome numbers

“…The monoploid genome size reflects evolutionary relationships in many groups of plants (e.g. Hohmann et al 2014, Krahulcová et al 2017. Among species of water-crowfoots, the largest 1Cx-values are for the pair of diploid species, R. circinatus and R. rionii, which corresponds to their isolated phylogenetic position in the sect.…”

Diversity in genome size and GC content shows adaptive potential in orchids and is closely linked to partial endoreplication, plant life‐history traits and climatic conditions

“…Nuclear genome size and genomic DNA base composition (usually expressed as GC content, that is the relative proportion of GC base pairs) are two genomic parameters that exhibit pronounced variation among angiosperm plants (Šmarda & Bureš, ; Dodsworth et al ., ), possibly with adaptive consequences (Bennett & Leitch, ; Šmarda et al ., ). Substantial evidence concerning the evolutionary significance of genome‐size variation has been accumulated, pointing to correlations with various structural and eco‐physiological plant traits such as cell size (Beaulieu et al ., ; Knight et al ., ), duration of cell division (Francis et al ., ; Šímová & Herben, ), seed mass (Beaulieu et al ., ; Krahulcová et al ., ), leaf persistence (Morgan & Westoby, ) and growth rate (Gruner et al ., ; Tenaillon et al ., ). The cumulative effect of these associations is likely to promote the involvement of genome size in more complex phenomena, namely adaptive evolution (Bilinski et al ., ), invasiveness (Suda et al ., ; Pyšek et al ., ), speciation and diversification (Kraaijeveld, ; Puttick et al ., ; Igea et al ., ) or global dominance (Pellicer et al ., ; Simonin & Roddy, ).…”

Biological Flora of the British Isles:Aesculus hippocastanum

“…Aesculus hippocastanum has a comparatively small nuclear genome size for a woody angiosperm at 1.22 ± 0.010 pg (2C), but such a small genome size is not unusual among woody species with large seeds (Krahulcová, Trávníček, Krahulec, & Rejmánek, 2017…”