Sam Gregory wrote this post as a project for Dr. Stacy Krueger-Hadfield’s Scientific Communication course at the University of Alabama at Birmingham. Sam earned a BS in biology and BFA in studio art from Birmingham-Southern College, and is currently pursuing an MS in biology at UAB. He is fascinated by Alabama’s diverse ecosystems, particularly the currently-threatened arthropod communities that serve a foundational role in these systems. Since starting graduate school, he has focused on studying both ecological systems and molecular techniques in order to equip himself for future research.
The valley which lies where India, Pakistan, and China converge has a problem with invasive species. This is unsurprising, as many regions have such issues. More surprisingly, though, is the species which has invaded – daffodils.
The phrase “invasive species” is an evocative one, conjuring imagery in the minds of all who hear it. Someone from Alabama might think of the Kudzu strangling out roadside forests. Someone from Australia might envision a swarm of toxic cane toads. Myself, I picture the privet and fire ants in my back yard, because I’m writing this during the COVID-19 social distancing period and trying to occupy myself with yard work.
These species are united by their undesirability. Kudzu destroys native plant life (Winberry and Jones 1973). Cane toads poison Australia’s fauna (Somaweera et al. 2011). Privet repopulates aggressively when killed (Hanula and Horn 2011). Fire ants are aggressive, with a sting that lives up to their name (Solley et al. 2002). With species, such as cane toads or kudzu, their introduction to new habitats was well-documented. They caused enough issues that their spread was noticeable not just to scientists, but to everyday inhabitants on the borders of their expanding ranges. Species such as this often have excellent records of their invasions (Winberry and Jones 1973). But not all invasive species were introduced in organized, documented initiatives, only to rapidly reveal their negative effects to any casual observer.
This brings us back to those invasive daffodils (genus Narcissus). Members of this widespread genus produce an attractive flower, are easy to keep, and spread readily to produce an attractive garden. For this reason, daffodils are among many attractive options for importation (Aslam et al. 2010). Unfortunately, some of the very traits that make them desirable mean that non-native daffodils can spread beyond the confines of their gardens (Rotherham 2005). This poses a potential threat to the native floras.
This is the tricky thing about invasive species lacking detailed historical records. In the absence of such records, how confident can conservationists be that a plant isn’t supposed to be there? Some reports have listed Narcissus species as native to the region (Mumtaz 2015), and others as invasive (Khuroo et al. 2007). This is where Mohammed et al. (2020) come in.
The researchers wished to evaluate the diversity and population structure of the Narcissus species in this region, with a particular eye toward diversity between the patchy clusters the flowers tend to occur in. This information could help cement the species’ nature as invasive as well as provide some insight on the invasion itself (Mohammed et al. 2020).
To this end, they examined five Narcissus species, collecting 40 samples in total (mainly from N. pseudonarcissus, from which they collected 24 samples). These samples were genotyped at 13 microsatellite loci, analyzing their diversity via a dendrogram as well as principal components analysis. The results revealed a surprising level of diversity. All microsatellite loci showed a high degree of polymorphism, and the dendrogram also showed a high degree of diversity, with species not clustering together and even individual sites only showed partial clustering in one instance. Similarly, the principal components analysis showed high variance, with no evidence of grouping by species or geography (Mohammed et al. 2020).
What can be learned from this?
Well, if these daffodil species are invasive, they have likely been introduced multiple times or been in the region for a relatively long time. Given what we know about the species’ ornamental value and the region’s history, both would likely be the case. This also means that it’s fairly difficult to demonstrate that a species is invasive without detailed historical records if multiple introductions occurred or if many generations since introduction have allowed further diversification. Though their results are inconclusive, Mohammed et al. (2020) have made crucial early strides in understanding the details of this species complex and its foothold in the region.
Hanula JL, Horn S (2011) Removing an invasive shrub (Chinese privet) increases native bee diversity and abundance in riparian forests of the southeastern United States. Insect Conserv Divers 4:275–283. https://doi.org/10.1111/j.1752-4598.2011.00131.x
Mumtaz AN (2015) Emperor Jahangirs method of observation and approaches to investigation of Kashmir ecology: An appraisal of his deep sense of sensitivity towards nature. J Ecol Nat Environ 7:72–80. https://doi.org/10.5897/jene2015.0505
Somaweera R, Webb JK, Brown GP, Shine RP (2011) Hatchling Australian freshwater crocodiles rapidly learn to avoid toxic invasive cane toads. Behaviour 148:501–517. https://doi.org/10.1163/000579511X565763