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Invasive alien plant species pose a global challenge, and their impact is amplified by
globalisation and the accelerating pace of climate change. In mild-climate regions,
drought-tolerant invasive plants showing broad environmental tolerance have a
competitive advantage. One example is Kalanchoe ×houghtonii (Crassulaceae),
popularly known as “mother of millions”. It is a hybrid resulting from the interploid cross
between K. daigremontiana and K. delagoensis, both native to Madagascar. Kalanchoe
×houghtonii, propagated as an ornamental plant, has emerged as a global invader in
less than a century. Four morphotypes of this hybrid have been identified, with different
ploidy levels and varying invasive capacities. Here we aim to investigate the genomic
variability behind the invasion success of Kalanchoe ×houghtonii. We sampled 57 acces-
sions of Kalanchoe ×houghtonii, K. daigremontiana, K. delagoensis and closely related
taxa, including old herbarium materials, from all over the world. We analysed genome
size, chromosome numbers, sequenced the whole genome, analysed the complete
plastome sequence of each accession, and studied the diversity of the ribosomal RNA
genes. We also performed a detailed phylogenomic study using nuclear BUSCO genes.
Our study reveals the genetic and cytogenetic variability between morphotypes and
shows that a single clonal tetraploid genotype (morphotype A) dominates all popula-
tions, emerging as the first reported clonal hybrid capable of worldwide colonisation and
invasion. Morphotype A shows a striking genetic uniformity, high phenotypic plasticity,
and extremely high rates of vegetative reproduction, representing an example of a
“general-purpose genotype”. The astonishing reproductive capacity, broad adaptability
and the speed at which K. ×houghtonii is colonising new regions by clonal spread high-
light the importance of understanding hybridisation and polyploidy in the invasion of
ecosystems. Our findings call for the need for risk assessments before developing new
hybrids for ornamental plant breeding that may exhibit invasive characteristics.
Citació
Botany 2025: botany without barriers (26-30 July 2025, Palm Springs, USA)
Condicions d’ús
info:eu-repo/semantics/openAccess