plants Article Influence of Habitat Types on Diversity and Species Composition of Urban Flora—A Case Study in Serbia Milan Gliši´ c 1,2, *, Ksenija Jakovljevi´ c 2 , Dmitar Lakuši´ c 2 , Jasmina Šinžar-Sekuli´ c 2 , Snežana Vukojiˇ ci´ c 2 , Milena Tabaševi´ c 2 and Slobodan Jovanovi´ c 2   Citation: Gliši´ c, M.; Jakovljevi´ c, K.; Lakuši´ c, D.; Šinžar-Sekuli´ c, J.; Vukojiˇ ci´ c, S.; Tabaševi´ c, M.; Jovanovi´ c, S. Influence of Habitat Types on Diversity and Species Composition of Urban Flora—A Case Study in Serbia. Plants 2021, 10, 2572. https:// doi.org/10.3390/plants10122572 Academic Editor: Robert Philipp Wagensommer Received: 26 October 2021 Accepted: 13 November 2021 Published: 25 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Academy of Applied Studies Šabac, Dobropoljska 5, 15000 Šabac, Serbia 2 Faculty of Biology, Institute of Botany and Botanical Garden, University of Belgrade, Takovska 43, 11000 Belgrade, Serbia; kjakovljevic@bio.bg.ac.rs (K.J.); dlakusic@bio.bg.ac.rs (D.L.); jsekulic@bio.bg.ac.rs (J.Š.-S.); sneza@bio.bg.ac.rs (S.V.); milenatabasevic@gmail.com (M.T.); sjov@bio.bg.ac.rs (S.J.) * Correspondence: milanglisic88@gmail.com Abstract: The aim of this study was to investigate the floristic composition and diversity of seven urban habitat types in 24 Serbian cities with different climatic affiliation. In each of the 24 cities, we selected 1 ha plots representing a habitat from one of the following groups: square, boulevard, residential area with compact and with open building pattern, city park, and sites with early and mid-succession vegetation stages. All vascular plant species that occur spontaneously in these plots were observed. Data on the main climatic characteristics were collected for each plot, and data on the life forms were obtained for each species recorded. Diagnostic species were identified for each habitat type analyzed, and alpha, beta and gamma diversity were calculated. A total of 674 taxa were recorded in the studied area. Significant differences were observed in habitats by diagnostic species and by life form representation. The lowest alpha and gamma diversity and the dominance of therophytes were observed in habitat types with intensive anthropogenic impact, whereas the highest number was recorded in mid-successional sites and residential areas with a compact building pattern. The analysis showed that habitat type influences species composition much more than climate. Keywords: species composition; richness; urban areas; anthropogenic impact; climate 1. Introduction Human activities are an inseparable part of urban area and play a leading role in modifying its ecological characteristics, forming similar conditions in diverse, often remote areas. Hence, the similar urban habitats are found in the vast majority of cities, even in areas in different biogeographical regions, with different macroclimatic characteristics [1,2]. Large-scale introduction of species with the cosmopolitan type of distribution, sometimes associated with a decline in native species, may lead to a further increasing similarity in species composition between regions [3,4]. Additional homogenization is caused by the presence of invasive species, primarily archeophytes, whereas neophytes mainly lead to opposite effects [5,6]. However, both groups of invasive species have been shown to contribute to an increase in the richness of plant species in urban habitats [5,7]. Namely, according to Pyšek [8], archaeophytes and neophytes account for 15% and 25%, respectively, of the urban flora in Central Europe, although the negative effects of alien species on native diversity have also been observed [9]. Additionally, urban areas are very heterogeneous, so this also contributes to a larger number of species in cities [10,11]. This heterogeneity, caused by different disturbance regimes, induced differences in species composition [12]. Simultaneously with the certain similarities and the number of generalist species found both in and outside the cities, pronounced differences can be observed compared to the surroundings, wherefore the cities can be regarded as a kind of ecological island [6]. Plants 2021, 10, 2572. https://doi.org/10.3390/plants10122572 https://www.mdpi.com/journal/plants